G-WAGON
G-WAGON
(weird - I posted a couple times on this thread yesterday and all of them are gone now.)
A good place to start is www.clubgwagen.com. they have a classifieds sections. Another is the G-wagen forum of www.pointedthree.com
Both have tons of G-specific information and with a search, you can find answers to most of your G-wagen questions.
As for benz tax - some parts are as cheap to maintain as the average mercedes sedan while others can get very expensive if left unmaintained. (A good G-wagen is going to cost much more than a good 123)
Also, it's important to find a mechanic who knows how to work on them. the engine and tranny are familiar to most mercedes mechanics but the rest tends to be easily misunderstood and improperly maintained. Suspension is totally different and the issues that come with 4WD are going to be totally new to a w123 owner.