I can add alot to this but I will get back to you later on this as I am t work. so here is the Q&D
The short of it is they are great cars with some know and well docments quirks that any DIY GRM person can deal with. The issue is that for the most part these were not purchese by car people and as such got a bad rep.
Early cars up to 03 and a viscous transfer case that was more fun to drive but was more prone to fail. they were under designed for the cars weight. hte 04+ ones are direct gear drive units that are more robust but still dont like being hammered on (no neutral to drive drops) And they are a NLA part so you will have to get a used one if you want a replacement.
Get the newest lowest millage one you can find and then do a complete fluid change using Amesoil products. the driveline fluids are suposed to be for "the life of the car" what that means is that when they wear out and should have been surviced the car is instead scrapped as something brakes. So ya they last the life of the car or in many cases the car lasts the life of the fluids in the driveline.
The shop manual calls for fluid changes every 30-40K (for severe duty) meaning if you actually drive the car you should change them every 30-40K. This is for the dif, the transfer case and the transmission.
When purchasing one look at the rear seal of the transfer case and make sure it is dry. If it is wet move on. They only hold about 3/4 of a quart in them and when they start leaking they go dry and fail fast. It is good to keep an eyen on these. Inspect with every oil change.
There is a nown issue with these cars going in to safe mode. I have found that it is 99.9% of the time caused by either the sensor on the throtal going bad or the sensor on the throtal plate going bad. It is a drive by wire system with redundency but it only takes one part to fail to kick it in to dafe mode. Many actually wrongly atribute this to a transmission failuer. It is not. the trans goes in to safe mode and will not come out untill the fault in the fly by wrire trottle system is fixed.
These cars are VERY sensitive to alignment and will eat tires if it is out.
Ware items include
tie rod ends
ball joints
rear upper link bushings
All should be looked at and serviced BEFORE you start going through tires in an alarming rate.
the rear camber is adjusted by moving the whole rear subframe. Closely inspect any car you are considering for the rear having excessive rear camber. this could indicate a rear hit of some sort. In some cars I have seen it just developing excessive camber and I really don't know why. There is a simple fix that involves swapping out an adjustable arm from a Volvo (V50??) that allows for easy rear camber adjustment. I actually had resigned a replacement in 3d Autocad hat I was going to get made but with my car getting totalled it became a moot point.
All this is easy stuff that can allbe handeled in your driveway. They are relaxing comfortalbe cars that do a great job of eating up the miles. They also handel very well for wha they are. I like to say they are not as soft as a Merc but not as sporty as a BMW.
I will post more if I think about it,
Ohya the headlight adjusters are a known failure point the plastic screws dry and brake causing you head lights to loo everywhere but down the road. I just took bailing wire and wired them in pace inside the housing and then put the covers back on. There are repair kits out there but I never tried them.