I've got an 06 Navara D40 Outlaw. Great car. It serves my needs and gets used to it's potential. In terms of tinkering I'm not the best person, especially as mine's still under warranty. It is all very ECU integrated with lots of plastic coverings to everything though. All I've done is towbar, A/T's, sound system really. The best place for info is nissan-navar.net but unfortunately it's all down at the moment as apparantly it got accidentally deleted. Should hopefully be back soon though.
Things to check when buying mainly would be the 4x4 including low ratio, most people won't use it and there has been a problem with one of the switch sensors on some batches I believe.
Hope that helps. If there's anything else that I can help with I'll try my best.