I will let the more knowledgeable respond, but from my experience with 2 LR4's:
Whomever wrote that posting has little to no knowledge of Rovers and probably has no idea what "normal" is.
It is true that multiple error codes can result from one issue, but:
HDC is hill descent. It works the brakes when going downhill off roading (and it works great!), but a error could mean brake problems with the actuators and or the computer.
Error code could also mean it has had a hard life.
Special Programs, from a quick search of other postings, is the suspension and may indicate that the compressor and or shocks, and or the valves are not happy.
Cruise Control Not permitted may be the clockspring in the steering column
At 167K I would bet that the transmission fluid, and probably the coolant have never been changed, who knows about how often the oil has been changed. (especially with 6 owners)
All of which are issues.
If you can get a title report you can find out if that's actually 6 owners or it has been owned by several dealerships as well along the way.
6 actual owners would concern me.
Look at the tow points at the rear - that's the main cluster in the middle and the two slots in the frame on either side.
Any damage shows abuse.
Look at the skid plates and at the bottom of the engine compartment - look for evidence of water as evidenced by rust or particulate/dirt/mud in places is should not be.
If it's been mudding that's very hard to get totally clean, and could indicate a hard life.
Raise and lower the suspension (foot off the brake), should raise from access to normal in 5 or so seconds, and same to off road height.
If it creaks, it has not been used enough (problem), if it's slow it may have been used alot (problem).
if slower then needs (or will need) a compressor, if it doesn't work at all, then any of the above, probably starting with the compressor.
Drive it slowly with wheels turned at/near the locks, if it's even a tiny bit jerky (and not glass smooth) then it's a transfer case problem
Drive is 1-2 mph then brake hard. A clunk means lower control arm bushings (I am doing that right now on the 2013).
Then there are all the cooling system issues at that mileage.
Timing chain tensioners? I'm not sure about 2005, but that's a catastrophic failure or an expensive preventive maintenance issue.
Sounds like a project vehicle.
Depending on how much you want to correct, and how deep into preventive maintenance you want to go I could easily see $10-15K in the reasonably near future if you do the work yourself.
In my experience my LR4's are (in general) easy to work on yourself.
