It's one of the easiest things to do on '80-96 trucks. Unclamp the heater hoses & point them up so they don't drain, remove the glove box, remove ~7 screws & the heater core cover, pull the heater core out. 30 min. total if you're slow. The hardest part will be the 3 phillips screws in the bottom of the glove box; a stubby works, but an offset is better.
