Extended turn-off time of dome light

I just looked at a wiring diagram there is an "interior lamp relay" that one would imagine is the most likely cause for this problem, I cannot find a location for this relay, in the workshop manual but maybe the parts department can tell you where it is from there parts micro-fiche.

I drive a 98 B4000 and I was having the same problem. There is an easy fix though. Spray some WD-40 into the door hinge (on the actual door itself) and let it work through. The switch probably just needs some lubrication. A cheap fix for you.