Brad,
If I buy a GM, it's likely to be one of the 1500s from the 2000s. How much of the above (and your other musings) would you think apply to those?
Plan on headlight assemblies. No getting around the plastic hazing over time. It's just what they do. At this age they are probably oxidized so thoroughly that yellowing and hazing can no longer be polished out. Might as well plan on tail lights while you're at it. They're bad about it, too.
Everything else is a maybe. If the truck has been well-maintained and necessary repairs done in a timely and complete manner, you may be okay for a while.
Depending on age, miles, and use, transmissions are another thing to keep an eye on. I'm not very up to speed on Chevy transmission from that time but I think that was the 4L60/4L80 era. They are both good trannys but, as with all slushboxes, they need to have been serviced regularly and not abused. See if you can get records. If not, take a good look and sniff. If the fluid doesn't appear sparkly or smell burnt and the trans seems to shift okay, you're probably okay for a while. However, if it's had a recent service this method won't give you much info.
In the end it's a twenty year old vehicle. It's gonna have problems, it's just a matter of how many and what kind. Mostly it's a matter of how the truck has been cared for. If the owner had problems repaired promptly, was conscientious about maintenance, and proactively addressed any potential known problem areas, they are as decent a used truck as you can get. If something does fail, there are a billion of the things on the road and GM used that powertrain for a lot of years. Most issues are relatively inexpensive to address, used parts are dirt-common, and new parts are readily available. A decent set of tools, YouTube, and LMC Truck are your friends.
Brad