I'd make sure the car has a service history that backs up that mileage these cars are easy to clock and hide mileage well.
The V6 is a great engine with few mechanical problems however overall Mercedes reliability is only so so.
I've just got the British magazine "Parkers price check" NOV 04 which this month has an article on the 20 most reliable cars.No mercedes gets into the top 20! The
results come from a combination faults recorded on 600,000 flleet cars between 1 to 3 years old and the JD Powers private owners satisfaction survey.
The best European model rankings are;

5) BMW 3-series
9) BMW 5-series
14) Jaguar XJ
18) Audi A4
19) VW Golf
20) VW passat

It may be worth getting 3rd party mechanical insurance.Here in the UK a years
cover(parts and labour) for engine,gearbox,recovery etc. is £250 even on cars up to 144,000 miles.

Re- changing the oil in the 722.6 gearbox I checked the past invoices on my
own car and the oil has been changed every 30,000 miles by 2 different Merc main dealers.This gearbox is not filled for life according to Mercedes UK,and they should know what there talking about as the UK is the third biggest market for new Mercedes.

adam