The bottom ends of the 3.0 are s solid as the the 22r(s), good for several 100k providing you do simple maintenance.  I have right close to 190k on mine, and no problems w/the bottom end, comp is still on the high end of oem specs.  My sisters had 225 on her '95 Runner before she ran it low on oil and it developed a knock.  She had a leaking valve cover that she never went back to a dealer for(developed not long after having the valves shimmed), and didn't check the oil level before the light would come on.  I could say typical female driver, but now a days it seems to be more a typical driver behavior issue than gender.

The head gasket has been an issue do to the EPA not allowing asbestos HG's, and Toyota didn't do a re-torque spec for the non-asbestos HG.  There was a recall campaign notice for the 3.0, take the VIN# to a local dealer and see if the HG recall has been done, if not, you may still be able to have it done, providing your block was part of the recall.  On;ly a certain series of engines was involved, and if it has been into the dealer for headwork, it should have already been taken care of.

The other issue w/the 3.0 is the tendency to burn an exhaust vale on the the #5 & #6 cyls.  The oem manifold set-up, plumbs the heat from 1,3 into 5 before dumping into the #6(which also has 2,4 plumbed into it).  The fix appears to be running a set of headers.  I had two burnt valves one in '98, and again in '04.  The first valve job was done by the dealer.  The second time I performed the rebuild and installed a set of Downey headers and had the exhaust valves shimmed a little loser than specs, so far so good. 

The 3" BL will be a blessing if you decide to rune headers, firewall clearance is tight w/the headers, and w/the BL you can do most of the work through the wheel wells.

Gears.
With an auto you really lose what power is available w/the 3.0, so you will want to re-gear it if the PO hasn't already done so.  W/the auto you need to go one gear set higher than you would if it was a 5-spd.  For example, a 5-spd only needs 4.88's to run 33's for oem performance, while and auto needs to run 5.29's.  If you run 35's in the future, you will probably want to do a 5-spd swap, since 5.71 gears usually are recommended for wheeling.  Fortunately you have a truck and not a runner so the performance of the auto may not be as bad.