U-joint failures take out transmissions so no that one is not worth it.
The thing is the newest one you will get is 16 years old, it is going to need work. I have one and I like it, it is easy to work on and runs well. But I have done head gaskets, not hard just takes some time, and replaced the front drive shaft. Various sensors etc are starting to fail, but at 16 years that is expected as most have been in there for 16 years.
The #1 issue is the engine followed by rust if you are a so called rust state.
The engine is a full aluminum engine with steel sleeves, any significant over heat is likely to cause head gasket failure or warped heads. That is compounded by a temp gauge that is functionally an idiot light and higher than originally designed operating temps for emissions. Both of these are easily addressed.
Rust is in the rear of the frame and can be extremely significant it requires a cut and replace of that frame section - I do not know where you are but that is more a case of pre-purchase inspection
A few other things
Sunroof drains and sun roofs are known to leak
Ac drains can clog
Drive shaft - remedied by getting a serviceable drive shaft and actually greasing it
"3 amigos" ABS wheel sensors and pump can throw a code, and you need an LR code reader to correct you still have braking just no ABS or traction control
Transfer leaks from the front input shaft -any LR with same transfer case can have the same leak it both a seal and shaft problem. Generally the solution is to just top up the TC when you do you oil changes the seal will never fail it will just leak
They need 91 octane fuel and the mileage sucks 100 liter (25 gal) tank and I get between 250 and 325 miles to the tank
Regular oil changes 3000 miles 10/40 or 15/40 with 1200 PPM zinc old push rod tech easy enough to get
Lots of them tick, old school push rod V8's do that with age as long as you do not hear it the cab it is not generally much of problem but it an be
On the pro side they are comfortable and capable, tons of interior space.
If you are serious about a Disco II go here
https://landroverforums.com/forum/discovery-ii-18/ it is an enthusiast forum but you will get all the good and bad if you ask.