Keith,
What questions do you have about removing the A/C? If it's not working, it's probably already leaked the refrigerant out. You could remove the cap off of one of the refrigerant ports, and briefly press the center of the valve (like letting air out of a tire). If nothing hisses, it's empty.
You could either leave the evaporator in place (but it should be cleaned out), or you can replace it with an "A/C delete duct". Someone here, or on IsuzuPup.com would probably have that part.
The main mechanical challenge would be to find an idler pulley to replace the compressor. Some people mount a pulley on one of the holes in front of the compressor bracket. That will require a different size v-belt, but it works. If you brace the pulley bracket, avoid bolting into the thermostat cover, they crack easily.
The heater core was indeed challenging, but I think I could do it a LOT faster the next time now that I know what to expect. I wasn't aware that there are posts here about how to do it (for the 2nd gen LUV), but I guess there's a lot here that I don't know about. Since you've read some posts, what do you need help with? As you see, I'm avoiding the effort of writing a step-by-step procedure, as that would probably be redundant and lot of time.
But I'd be happy to help with questions. I will throw this in: If your manual says you have to remove the dash, get a different manual. That is NOT necessary.
Jack
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'83 Isuzu P'up Diesel LS - Original Owner
JoeIsuzu@IsuzuPup.comIsuzuPup.com