G400CD! G500

I am thinking of importing a 2000-2002 G400 or G500 from Germany and was wondering if anyone can assist with the following questions:

Are either of the engines prone to problems - it will have done something less than 125,000km and I am planning on running it for the long term but only doing about 10,000km per year. I thought I read something about the 400 engine to the effect that it had problems at about 100k;

Which it the best – it seems to me that the diesel will last longer and be better on fuel economy, however the 500 is a beast but not as much so as the 55;

When did MB start putting in their own interiors – I read somewhere that pre ’99 500s have an AMG interior which is far better than the one now fitted by MB (there were a number of complaints on a US website when the 500 was launched over there;

What are the relevant dates when the upgrades came out, indicators on wing mirrors etc;

Is it easy to import a G from Germany and register it. I know I will have to change the headlights but are there another things to watch for?; and

Any other tips comments?

I would be particularly interested to hear of any 400 or 500 owner’s experiences.

Thanks in advance.