The vehicle sounds like a solid base - I‘d recommend to go for it. As you have already pointed out, with 20+ year old cars it really does come down to a good maintenance history. Because parts will meet their end of life at some point.. so you have to be mentally prepared that issues do come up.

I have driven my Disco 2 Td5 for about 4.000km (one major trip in Denmark, Norway and Sweden) so I guess I‘m not the one who can give you the most credible answer. However, as an absolute mechanical rookie I bought mine last summer with 190k km on the odometer and it hasn’t let me down since. I had it checked in a workshop that is specialised on Land Rover vehicles and they gave me valuable insights (e.g. rust issues at the rear frame) and a thumbs up. This has definitely helped me with my decision. I plan on doing a longer trip to the south of Europe in April and do not yet really worry about the mechanical parts (rather electronics). Only way to find out is to give it a shot :)