The dealer should be able to run the VIN and tell you if the head gasket recall has been done. Some people make it out to be more of an issue than it really is. Yes, the 3.0 is kinda underwhelming in power and fuel economy and the design wasn't Toyota's best, but it's no worse than any of the domestics.
3.0 = 3VZE engine
3.4 = 5VZE engine
Honestly, if you've built other rigs, this should be no different. The IFS is reasonably stout and should be able to handle 35's with no problem, but of course you'll want to regear if you decide to go that big. I think you should be able to fit 32's with no lift, using a ball-joint spacer lift or cranking the torsion bars for 1" lift should get you into a nice set of skinny 33's