The EGR valve is located on the front of the engine, just behind the altenator on the "right" cylinder head. Right is as seen from sitting in the driver's seat. There should be a tube going to it held on by 2x 8mm bolts and the valve itself is usually held on by 2x 10mm bolts. According to the factory service manual, you can remove it without taking anything else off. I've yet to replace an EGR valve on a hemi motor yet (I've been at an independent shop for a while, no longer at the dealer) but I do know in other applications they CLAIM it will just come right off but in actuallity, other components have to be moved first.
The valve looks like a small coke can. It will have a 5 wire connector on the top and bolt to the head on the bottom. If you've searched online for replacement valves then you'll probably recognize it once you see it.
The electrical connector will have 5 wires in it. The following information is based on the ignition switch being in the "on" position with the engine running or not.
--Dark Blue/Dark Green is the sensor ground, DO NOT use a test light to check this, only a multimeter.
--Dark Blue/Violet is the EGR solenoid Control. This should have power on it when the EGR valve is being commanded on. Without a scan tool to actuate the EGR valve, you won't be able to verify this.
--Black/White is the ground for the Control circuit. It appears to go to a chassis ground so you may use a test light (clamped to battery positive) to verify this wire.
--Yellow/Pink is the 5 volt supply wire. You should see 5 volts on it all the time.
--Dark Blue/Light Green is the EGR signal wire. With the sensor unplugged, this will show 5 volts. The computer puts out 5 volts on this wire to check to see if the sensor is unplugged. Once the connector is plugged in then the 5 volts drops down to whatever the signal voltage should be based on EGR valve position, you may be able to remove the valve from the head, plug the valve back in and move the small plunger by hand and watch for a voltage change on this wire. I've not done this before but logic would suggest that a functioning valve would report a voltage change. It's possible that your old one won't report a voltage change and that's precisely why you are having problems with it in the first place.
Let me know if you need additional assistance.