I found a superchip on cl for $200. It says it will work on a 98-03 magnum 318. Did they change something in 98 or will it work on my 97?

 

Won't work because SuperChips doesn't make a '97 or older tuner...
For $65 more you can get a custom tuned SCT anyways

 

Buying tuners used is a crap shoot. If the seller didn't put his truck back to stock, the tuner will be vin locked, and won't work until you crank out some more money to superchips to unlock it. You would, in the end, spend LESS money just getting a NEW one from hemifever.