Condition and spec are probably the biggest things to look for. All the oily bits are fairly easy to change. Biggest hassle is rust, so as others have said, chassis is number 1, bulkhead number 2, as these are the main places you get corrosion on a Land Rover.
These bits are still fixable, but take more effort and money.
Swapping in another engine, gearbox, axle is relatively easy and cheap.