Well I've had 3 of em, and out of them 2 were great 1 was a pig! Had issues with the air-suspension with 2 of them but if you can DIY its easy and is really just basic plumbing. The bags are easy to replace and usually if you look at them you can see where they start to wear / perish, its where they fold under at the corners. If the car is left for a day or so and drops to its bump stops then there is a leak somewhere in the system. If there are leaks then (as I found out) the air-compressor starts to work over-time and overheats & the piston ring melts. Can get new ring kit on Ebay for £25
Engine wise my 4.6 was lovely but same as the Omega the coolant should be clean and a nice red colour. Both the 4.0 & 4.6 have form for over heating, usually this is due to blocked rads / or water channels. So keeping on top of the coolant is a must. On 2 of mine the nearside bank cylinder head gasket started leaking right at the rear of the engine, apparently this is quite a common place for them to go and a weak spot, so check for any weeps or leaks.
HEVAC systems can be problematic, blend motors pack up sensors on the AC can go give annoying messages, but again are easily sorted with a bit of know-how.
You can get Hawk-eye (diagnostic kit) for your model if your serious on keeping it and it can read pretty much all of the modules and I found it en valuable just as much as this site
http://www.rangerovers.net/index.htmlWould I have another?? Oh yeah! too right I would, loved every minute of owning them, excellent tow car and phenomenal off road. Nice ride position, plenty umph & effortless. Much better than an X5 that gets stuck in a grass field