2000 saturn sl2 problems

My girlfriend just bought a 2000 Saturn sl2 from a local dealorship with 93,000 miles. The car is in perfect shape, and it ran perfect on the test drive. Now, 2 weeks later it is having a whole mess of problems. The service engine light came on and the autozone guy told me it just needed new plugs and wires. I changed those and it seemed to run perfect, the light was reset, and we thought all was good. Ten minutes later it started to shift real hard, throw you back into the seat hard (it did this before we changed the plugs too) and the engine temp gauge stops working and the service engine light is back on again. What should I do? Any ideas?

Lemon Laws apply to where you are?

no, of course not. That'd be too easy. We called the dealorship though and explained what's going on and they agreed to have an outside mechanic take a look at it and they'd cover the costs.

Lemon laws only applys to new cars no more then 12 or 18 months old, depending on state

please let us know what the shop finds