I’d be looking for cracks and welds where they don’t belong: steering components, axles, 3 point lift arm mounts on the tractor, and particularly the toplink mount on the tractor. Used improperly or a bit carelessly, a winch can put quite a lot of force on the toplink.
If it has a loader, same thing: look for cracks and non-original welds. Get it somewhere flat so you can make sure it isn’t twisted or bent.
I would also run it through every gear (or range if HST) forward and back to ensure the transmission has no obvious issues.
Check fluids for contamination. If fluids and filters are pristine from recent change I’d think hard about passing; if recent change and hours don’t indicate time to change that would be a hard pass for me. Fresh paint is kind of the same, especially on a tractor with that type usage history.
Problem with using it as a skidder is it really depends on the operator, terrain, and load size how hard that is on the machine. Could be anywhere from moderate use to heavy abuse, so look hard for any signs of abuse and pass if you see abuse. And yes, I have a skidding winch so not throwing shade at winches.
Admittedly not an exhaustive list, but a few things to consider.
