The 2002s are sometimes known to have some rather funny electrical issues. Hopefully they were sorted out by the previous owner(s) $25,000 for one with over 100,000 miles is about what the market it dictating these days but still try to negotiate down (Do some research on the front axle service before you get stuck with a nasty repair bill)
I used to have an 04 and while it drank fuel like there was no tomorrow it was still a fantastic vehicle. Keep in mind that the steering is quite heavy and it will tire you out on longer trips.
Ohhhh dear is it this one?
http://www.autotrader.com/fyc/vdp.jsp?ct=u&car_id=278726947&dealer_id=55101935&car_year=2002&rdm=1273370839086&lastStartYear=1981&num_records=100&model=G_CLASSCLASS_SERIES&systime=&make2=&highlightFirstMakeModel=&start_year=1981&engine=&keywordsrep=&keywordsfyc=&certified=&body_code=0&fuel=&awsp=false&search_type=both&distance=0&marketZipError=false&search_lang=en&showZipError=y&sownerid=88841&make=MB&color=&keywords_display=&page_location=findacar%3A%3Aispsearchform&min_price=&drive=&default_sort=priceDESC&seller_type=b&position=top&position=top&position=top&max_mileage=&style_flag=1&sort_type=priceASC&address=06111&advanced=&end_year=2011&transmission=&doors=&max_price=&cardist=2019&standard=false
If so I would avoid it. Aftermarket wheels like that pound the heck out of the suspension........ It almost looks like a 2nd owner bought it and drove it till the warranty went out at 100,000 miles and then freaked out when they realized what it would be like to pay for repairs.