You can try replacing the normal tune up stuff first. This never hurts. Make sure you follow your normal service interval periods as well that are located in your owners manual. GM usually says there plugs are good for about 100,000 but some fail way before that period.
The problem could possibly have something to do with the throttle position sensor. If the sensor is faulty it could cause possible jerks or skips in acceleration. This is only a suggestion and the proper way to determine if it is faulty or not is to place the vehicle on a scan tool and do the required component tests. If you have any other questions, feel free to ask. Thanks.
The transmission filter should be replaced everytime the transmission is serviced. They most likely used a transmission service machine that doesn't require them to take off the transmission pan. This just replaces the fluid without changing the filter. If there was a transmission code then this could be a totally different problem. The mechanic will see if there are any codes stored for the transmission when he hooks it up tomorrow. If he does find any codes, have him write them down for your reference and let me know what they were. If you provide me with the codes I can tell you what could be causing them. Thanks.
This code is for the shift execution time. This code is set for the amount of time that it takes to execute a shift. The transmission pressure is modified by an Adaptive modifier which controls the shift execution time. If the shift takes longer than 0.65 seconds and the adaptive modifier cannot shorten this time, then a counter increases by one. If the PCM detects a counter value of 3 during one trip then the DTC 1811 will set. The diagnostic chart on this problem has so many components or faults that could be causing this problem. The only way to really tell what is wrong is to perform all of the steps of the diagnostic test with a scan tool. This will have to be performed at the repair shop. The shop will have to do this test in order to find out what exactly is the cause of the problem. They probably just suggested to replace the solenoids but I would make sure they have done the proper testing before they start throwing parts at it, hoping to fix the problem. Let me know if you have any questions. Thanks.