Very easy to fix - just did this on my son's '98....
- Remove the interior trim panel between the driver side front and rear doors (support pillar).
- Look down near floor at the seat belt retractor assembly.
- Find the little white electrical plug (DO NOT mess with the plug that has the YELLOW taped wiring - part of the crash protection system)
- Squeeze the small two wire white plug and it should pull off the retractor assembly.
- Two ways to fix the white plug to turn off the dash light
1. Get some stranded electrical wire (lamp cord is fine) and remove a couple of fine strands (maybe 3/4 of an inch long) and twist them together. Insert into the white plug connector -- idea is to short the two contacts together. You need fine strands so everything fits back together nicely. Plug the shorted connector back into the retractor assembly. This short makes the dash light sense that the belt is pulled out and being used. The belt switch gets worn over time and that's why the dash light comes on.
2. Get a short length of solid wire (or 1/2 inch piece of paper clip wire - non painted). Shape into a U form and insert into the white plug connector to short the two contacts together. Use some electrical tape to wrap everything up nice and tight - don't want the paper clip wire touching anything else. You don't need to plug the white plug back into the retractor assembly if done this way.
Replace the trim piece and you're good to go.