Your 97 is an OBDII vehicle. A thermostat witha lower temperature wil likely set a code and turn on the MIL. If you really think the thermostat is sticking closed, by all means replace it, but use the factory temperature.

Double check to make sure the fan really is working on the fastest speed it can. Perhaps when you set it up it wouldn't work on high speed and you never noticed.

If you haven't ever replaced your radiator cap, do it now. They do wear out.

Lastly, and most importantly, are you sure it's overheating? What is the temerature of the coolant when it starts spewing? What does the temp gauge say is going on?