That's so true about those things crapping out in the middle of winter. I did this same repair on a 2000 S-10 so the vehicles are pretty much identical. My story goes like this: Heater core failed, I took the pickup in to the shop since I didn't want to spend the time fixing it and wasn't sure I could do the work properly, was quoted over $1,000 to fix
, decided right then to do it myself and told the service guy no way I'm paying that, I'll buy the part and do it myself. His reply was "if you can replace this by yourself, you have a job here."
Challenge accepted! I did fix it and promptly made the drive back to the shop and placed the junk heater core on the counter in front of the same guy and told him I didn't need the job.
I did the work with nothing more than normal garage tools and a Haynes manual. Just take your time and pay attention to all the stuff you need to unhook. I won't lie - it's a process. I had to remove the entire dash from the vehicle. That is actually easier than you'd think but you have to unhook the steering column and lay that on the seat, then go about unplugging the air bag connectors (not sure if 97 even has air bags) as well as the multi pin connectors for all the dash electronics. There are 4 or 6 bolts at the top of the dash near the windshield. Remove those and then the dash pivots (PIVOT!!!!) forward so you can remove the remaining clips and plugs. Then remove the dash via the door of your choice. Have a friend handy to help lift that damn thing and move it. From there it's fairly easy to deal with the heater core. I do remember 1 bolt being inside of a plastic box inside the engine bay where the heater core pipes pass through the fire wall. There was an access hole to get to the bolt but the engineer who designed that must have had 2 year old toddler hands. I could NOT reach in there to deal with that bolt. Had to go bribe wife to stab her small hand down there and remove/replace the thing. 80% of the time involved was dealing with the dash, 20% was actually spent dealing with the failed part.
It took me 2 solid days to complete the repair. Keep that in mind. I would say the little plug-in heater is a good idea until you know you have a chunk of time to spend working on the fix. There were no special tools needed that I can remember. The Haynes manual did a decent job of walking a person through the fix and had good pictures showing where the plugs and connectors are behind the dash. I had no prior experience with that sort of repair and came away with no broken bits or extra parts. I'd say you can fix it.