I would offer $1k and see if he takes it, you shouldn't have to pay much more than that. A rebuilt/new replacement engine is going to run upwards of $1900. If it is an auto, and you can/willing to learn to drive a manual, pass on it, the 3.0 behind the auto tranny is gutless.
I'm not much of a mechanic, but I could swap an engine.
Do you mean pull out the one in it and put another 3.0 in, or swap in something like a 4.3 Vortec or 3.4 Tacoma engine? If the latter, you have the ability to rebuild the 3.0 that is in it. Tearing down a 3.0 isn't physically hard, just mentally, i.e, a lot of vacuum lines, hoses, wires etc to take off and keep track of. If you do decide to rebuild the 3.o let us know, there are a few of us here that have rebuilt one and can give you help/hints on things to do that make there build a lot easier.
Difference between wheeling a truck and a Runner, not much in the ability of each, but the Runner is heavier and has more sheet metal and glass to get banged up, and the '93 Runner has coils(rear) springs rather than leaf which makes lifting it a little more expensive than the truck. Also fitting larger tires is harder on the 2nd gen Runner, since you can't just cut the rear fenders, well you can, but then you have more work to do.
Not sure if this is near you
http://knoxville.craigslist.org/car/605762826.html. It needs engine work but if you are looking to build a beater rig for the woods this is a good start. The x-cab on the 2nds gen trucks isn't as large as on the 3rd gen trucks though, but it is straight axle and it is geared for 33's, add a flatbed and you should have a good starter rig.