If as clean as described, price is right, only "potential" flaw, and for how you plan to drive you would most likely never use it anyway. As for operation - if not a landcruiser owner/tech good chance they don't know the rear diff lock only works when the transfer case is in low. And as stated if not used for a long time need to slowly drive it around a bit to get to engage. Best done on a dirt road so you can make some s-turns. A major no-no on asphalt as both the rear and center diff's will be locked at that point and you could start breaking things if not careful.
Good luck with the purchase - 90k on that truck means it has barely been broken in. I would ask about timing belt/water pump service as about do. If not done and you can do it yourself use as a bargaining tool on the price or plan on the $600-$800 for shop/dealer to do it.
