I came across a good deal on a 1998 STS but the trunk has a bad dent right on the edge by the 3rd brake light, so it isn't fixable. I did find a trunk from a 1993 sts, but I hear only a 98-00 will fit the 98. whats the difference on the 93? or a 01?

There was a body redesign in 98, as the STS moved to the G platform (as used on the Aurora). Not sure how the 01 differs, although the tail lights may have changed that year.