Rust is the main issue. Check spring perches, tops of doors behind the rubber seals, wheelarches, engine bay, behind the headlamps, boot (trunk) lid, etc.
Engines are bombproof - seriously, they're very very reliable. Mine burns no oil whatsoever, although there is about 7 synthetic litres of it
Diesel leaks are common, but easily fixed.
Timing chains last forever.
ATF likely won't have been changed, but its not a difficult job to do, and should be done.
Engine mounts will be going at that age, again, not a difficult job.
ARB drop links go, but are very cheap to replace and require no specialist tools.
MAF sensors are a common fault, but not expensive to replace and take about 2 minutes to change.
They're good cars, but don't expect trouble free motoring. They're complicated and expensive cars, but they're pretty easy to work on, and the standard of engineering is generally very high. You would be well advised to buy a metric toolset though.