$2800 for a California 4Runner is a good deal, you would not lose money in the long run. They are a good platform build on, depending on how much your "mild/moderate" build up you need. I build my daughters '85 as a moderate build, and I still replaced the Steering box, replaced the front spring hanger, 3" front springs (TG), Moved the rear spring hanger forward (longer Allpoo 4" springs) and a single 4.7 Transfer case. Lunch box lockers front & rear and 33" tires. That set me back decent amount of time & money, it's the little things that add up. The good news is it can do some of the Hammer trails, all of Big Bear trails, Dusy Ershim , Rubicon etc.
The first modification I would do is put armor on it before the body turns into a Raisin. just my .02$