I get this question a lot and it's tough to give a single recommendation because people's wants/needs are different. Overall, look for no rust, solid service history, and pay for a legitimate PPI who knows these vehicles.

You won't find a US G Class with a diesel. They started importing in 2000 and all have been petrol. You can find older imported models though if you're committed to that. I'd argue these v8s aren't overly complex. The 5.0L V8 in the 2000-2009 G500 is an excellent engine, and the G550 5.5L V8 is also stout as well as found in other models, so decent parts availability and serviceability.

For traveling, it depends on what you're used to. It's a 3 ton dual solid axle vehicle, and I've known quite a few bougie customers who purchased one blindly just because of aesthetics and trash the ride. I love how it drives, especially with the new suspension on it. Really comes down to personal taste but I've had three of these with maybe 100k miles across them and always felt comfy on trips.

As for accessories/aftermarket, it's a far cry from Toyota but it's becoming more approachable, but on average they carry a premium over Toyota goods. Jackwagon Overlanding has become such a great resource for the community, not just importing products but designing and manufacturing them to make some of these more approachable.

Feel free to DM if you have more questions.