Corey,
Thats really impressive (milage). As far as your cooling problem, yes you may very well be another victim of the clogged coolant system. I would recommend taking your radiator out and have it professionally flushed, or better yet, just replace it (if its original). Then look at your fan clutch, is it working? My 00' Xj clogged up at a mear 21k, replaced EVERYTHING, and now at 86k, still running great. Unfortunaly there is now flush kit on the consumer market that will clean a clogged system, I've tried, need to be done professionaly. As far as your oil issue, I would recommend getting some LUCAS Oil Stabilizer, and add a quart to your evisting oil. This will help to protect on initial start-up, or look into a Syn-blend oil such as Castrol. Good luck.