Repairs to 1996 Explorer:

I have a 1996 Ford Explorer XLT 6 cyl. With 126K miles. I am the original owner and have not had any major problems with it at all. I am taking it to a repair shop to have everything checked and fixed on it. Any things to watch out for from the repair shop?

If I am happy with this vehicle and want to keep it, what is the most I should invest in it?

Don’t let them hook up a U-Haul trailer to it. The truck will immediately do the mambo and go off the road.

On a serious note: Are you experiencing any problems right now? If not, be a little skeptical of any gloom-and-doom diagnoses. Skeptical doesn’t mean to reject the possibility out of hand. Just ask questions (and post the issues here).

Make sure it is a reliable repair shop which will be able to give you the actual degree of wear on various oitems. Sears Automotive, and some other chains, would immediately find $5000 worth of repairs. A AAA certified auto inspection centre will give you a good idea of what the car needs, it anything.

If you’re happy with it then repair any problems (within reason) and keep driving it. No reason why it won’t hit 300k miles.
Depending on the road and environmental conditions, I would have the suspension closely inspected (especially ball joints) and odds are that at 126k miles the belt tensioner pulleys could be getting a bit iffy. It’s always better to replace the tensioners and belts rather than wait until a tensioner seizes up and pops the belt in the middle of nowhere during a thunderstorm.

The fuel filter is another item that is often overlooked, or ignored, and can become a problem as far as fuel pump life is concerned.
Transmission fluid/filter change is always recommended (at 30k mile intervals).

I wouldn’t have a problem with investing a few grand in it if need be and IF the repairs are legitimate. The way I look at it would be if you bought another vehicle you’re going to lose a couple of grand right off the top and immediately. Even more if the note was carried to full term.