There is a real bad jerk when I put car in reverse and sometimes while driving.

Hello, There may be an issue with the torque converter, which is like the clutch for an automatic transmission. Does it clunk the second you place the car in drive, or does it clunk a couple of seconds later? The other thing I would suspect is the alternator or battery. Saturns especially, when they go into "safe mode", the transmission becomes violent, and I mean violent. Yet another possibility: the subrame bushings may be worn out, allowing the subframe to slam into the unibody frame when the vehicle is placed in drive. It makes sense that this would be the case since the car doesn't do it when it is cold (morning, sitting). Also, I had one of these, and I replaced them for the same reason. Test, Test, Test. These really are great cars, and failure is not typical, so don't throw out more money on parts without testing. If you have other questions, or need more information, let me know, otherwise, here is a list of certified shops in your area with the training to repair your vehicle: http://repairpal.com/saturn-within-10-miles-of-memphis-tennessee-38114