The P0756 is the 2-3 solenoid. The P0758, could be a wiring problem at the wiring harness pass through or it could be cause by the failure of the solenoid, but check the wiring close. You will need a class 2 scan tool to reset the memory values when you are done, but you should be able to do the job yourself. GM instructions below. Thanks

2-3 Shift Solenoid Valve Replacement

Removal Procedure

1. Remove the case side cover.
2. Disconnect the transaxle wiring harness.
   
   
   
3. Remove the 2-3 shift solenoid (315B).

Installation Procedure

1. Install the 2-3 shift solenoid (315B).
2. Connect the transaxle wiring harness.
3. Install the case side cover.

   Important: It is recommended that transmission adaptive pressure (TAP) information be reset.
   Resetting the TAP values using a scan tool will erase all learned values in all cells. As a result, The ECM, PCM or TCM will need to relearn TAP values. Transmission performance may be affected as new TAP values are learned.

4. Reset the TAP values. Refer to Adapt Function .

Hi again, The side cover is on the side of the trans, not the bottom oil pan. It is on the driver side and the drivers axle actually goes into it. It is a little more involved to remove than the oil pan. You can rent an engine support to do the job from a parts store. Info below on removal. It is a pretty big job and may require some special tools, you may even want to call around and see what a professional trans man would charge to do the job.

Control Valve Body Cover Replacement

Tools Required

1. Disconnect the battery ground (negative) cable.
2. Remove the throttle body air inlet duct.
3. Install the J 28467-A .
4. Install the J 28467-90 .
5. Install the J 36462 .
6. Remove the engine mount struts.
7. Raise and support the vehicle.
8. Remove the left front wheel.
9. Remove the left engine splash shield.
10. Remove the stabilizer shaft brackets from the lower control arms.
11. Remove the left tie rod end from the steering knuckle.
12. Remove the wheel speed sensor harness connector.
13. Remove the left lower ball joint from the left lower control arm.
14. Disconnect the left drive axle from the transaxle.
15. Secure the drive axle to the steering knuckle/strut.

    Caution: Failure to disconnect the intermediate shaft from the rack and pinion stub shaft can result in damage to the steering gear and/or damage to the intermediate shaft. This damage may cause loss of steering control which could result in personal injury.

16. Remove the pinch bolt at the intermediate steering shaft.
17. Remove the intermediate shaft from the steering gear.
18. Disconnect the three-way catalytic converter pipe to the right (rear) exhaust manifold.
19. Support the right side of the frame with jackstands.
20. Support the left side of the frame with jackstands.
21. Remove the transaxle mount bracket.
22. Remove the transaxle mount.
23. Remove the engine mount lower nuts.
24. Loosen the right side frame to body bolts. Refer to Body Dimensions, Frame and Underbody.
25. Remove the left side frame to body bolts. Refer to Body Dimensions, Frame and Underbody.
26. Adjust the jackstand to the lower left side of the frame.
27. Position the drain pan under the transaxle.
28. Remove the wiring harness connector.
    
    
    
29. Remove the case side cover bolts (56-58).
    
    
    
30. Remove the case side cover pan (53).
31. Remove the case side cover gasket (54).
32. Clean the case.
33. Clean the side cover gasket surfaces.

Tools Required

1. Install the case side cover gasket (54).
2. Install the case side cover pan (53).
   
   
   

   Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

3. Install the case side cover bolts (56-58).

   Tighten
   Tighten the case side cover bolts (56-58) to 25 N·m (18 lb ft).

4. Remove the drain pan from under the transaxle.
5. Install the wiring harness connector.
6. Adjust the jackstand to raise the left side of the frame.
7. Install the left side frame to body bolts.
8. Install the right side frame to body bolts.
9. Install the engine mount lower nuts.
10. Install the transaxle mount.
11. Install the transaxle mount bracket.
12. Remove the jackstand support from the right side of the frame.
13. Remove the jackstand support from the left side of the frame.
14. Connect the three-way catalytic converter pipe to the right (rear) exhaust manifold.

    Caution: When installing the intermediate shaft make sure that the shaft is seated prior to pinch bolt installation. If the pinch bolt is inserted into the coupling before shaft installation, the two mating shafts may disengage. Disengagement of the two mating shafts will cause loss of steering control which could result in personal injury.

15. Install the intermediate shaft to the steering gear.
16. Install the pinch bolt at the intermediate steering shaft.
17. Install the left drive axle to the transaxle.
18. Install the left lower ball joint to the left lower control arm.
19. Install the wheel speed sensor harness connector. Refer to ABS.
20. Install the left tie rod end to the steering knuckle.
21. Install the stabilizer shaft brackets to the lower control arms.
22. Install the left engine splash shield.
23. Install the left front wheel.
24. Lower the vehicle.
25. Install the engine mount strut.
26. Remove the J 36462 .
27. Remove the J 28467-90 .
28. Remove the J 28467-A .
29. Remove the throttle body air inlet duct.
30. Connect the battery ground (negative) cable.

    Notice: Do NOT overfill the transaxle. The overfilling of the transaxle causes foaming, loss of fluid, shift complaints, and possible damage to the transaxle.

31. Adjust the fluid level.
32. Inspect for proper completion of the repairs.
33. Inspect for fluid leaks.