Bobby,
First off, welcome to The Corvette Action Center.
I highly suggest you pickup an owner's manual for your '91. You can find them at either MidAmerica or Ecklers (both are listed on the Parts and Accessories page of this site.
You're 91 is equipped with an oil life monitor which needs to be manually reset each time you change the oil. Here is the procedure:
1. turn the key to the "On" position, but don't start the engine.
2. Press teh ENG MET button on the Trip Monitor and release it. Then, within five seconds, press and release the ENG MET button again.
3. Within five seconds, of Step 2, press and hold the RANGE button on the Trip Monitor. The CHANGE OIL light will flash.
4. Hold the RANGE button until the CHANGE OIL light stops flashing and goes out. When the light goes out, the Engine Oil Life Monitor is reset. This should take about ten seconds. If it doesn't resent, turn the ignition "OFF" and repeat the procedure.
Hope this helps.