Runner, congrats on your 97 GTS! The 97's were strong running cars -- definitely a good year. The problems Vipers of that vintage can have are Intake Manifold gaskets (TSB) and leaky engine seals. You should verify the IM gaskets were replaced per the TSB; almost all 97's built before mid-October 1997 had flakey gaskets. The leaky seals will show up as oil seepage under the engine. Neither of these are major issues, and are covered by the extended warranty. Good choice in upgrading the fan; it will make a big difference.
Also, bear in mind your tires are now 5-6 years old. While there is probably lots of tread left, they're surely getting a little hard by now.
Enjoy!