The ideal G for me would be a 2005 MY. I say that because even '04 had some electronic gremlins that some owners used to complain about. It's also the last year for the 5 speed transmission before they switched to the 7 speed which shifts roughly and by Mercedes standards is nowhere near as easy for servicing.
The '02 have smaller brakes which were upgraded in '03. The '03 also have the side markers built into the side mirrors, the '02 do not. Look out for paint flaking off the mirror posts or on the roof. In '07 they updated the center console slightly. It's getting harder and harder to find clean '02 with service records and many have between 120K and 150K miles now. That's a mileage range where there's greater potential for big ticket items to go bad if the truck wasn't maintained well. If you find something in the 80K-100K mile range you can probably get another 2 years out of the truck without major issues ($1K+) but I'm just generalizing. I ran my last '02 to 132K miles and it was going strong and I had complete confidence in it for another 20-30K Miles and wouldn't hesitate taking it cross country or deep into sticks but I had done a lot of preventive maintenance. Personally I would pay a little premium for the right truck (service records, '04+, mileage below 80K, no accident history, color I want, interior and exterior condition). An '03 would be my second choice.
