1994 Isuzu Trooper .. review from North America

I recently picked up a 1995 trooper with 200k on it. The vehicle seems to be in good condition. The only two concerns I have are, the truck starts to get hot and the air con doesn't work at idle while in traffic; and the check trans and trans oil light came on. The later of the two was the most concerning, the trooper would not shift out of first then it would shift hard I was able to get it home (I only went around the block) and it coulden't make it up the drive way! I parked it and started it up later and it drove great? The next day I got in and cranked it up and I was greeted with the flashing trans light, again. I added fluid and it drove great and still is for that matter, I drove it about 30 miles with no trouble in 100 degree weather no less. My question would be are these transmissions very delicate? Would being a little low on fluid cause this problem?