Only you can decide what makes sense for your budget and plans. However, in my opinion, I'd spend the $2k or so to fix the leaks, even the AC for a bit more. I look at cost per mile as my guide to repair or replace, vs. cost to repair vs. what it's worth. I doubt the engine needs overhauled -- just repaired -- long overdue maintenance type repairs.
After repairing the truck, start saving for a newer one as you suggest. 230k miles on a 7.3 --- why, I bet the engine could take more.
You mention your house will be paid off in 6 months. Again, IMHO, fixing the truck, start saving, and in a year or 2, you will be ready. You already mention a trip so not a lot of camping next year.
My opinion on this, by the way, stems from experience ... I've given up on a vehicle and next thing you know, I'm deeper in the hole, and the old vehicle has been repaired by someone else and still truckin'. Your experience and variables may vary.