My parents once owned a D2 (2002 facelift) went greenlaning regulary BUT always got pressure washed underneath after, to rid of the mud/salt etc. They all rust regardless, but if washed underneath it prolonges the time the tin worm can get to work and always best to underseal 'em if you can.
Needs a rear 1/3rd as it’s rotten under the springs cups. They’re a grand plus fitting. I don’t think it’s worth it tbh. Make as much breaking it. Especially as that was the original plan when I bought it anyway