Newbie Purchase Advice, Please

I've got a line on a great 300TD wagon; turbodiesel with around 250k; at 210k it had a new, rebuilt tranny installed by a MB dealer. Almost all receipts available from the life of the car; I've spoken with the owner and she's very nice AND informed about the car.
My question is rather simple: if a car has been dealer-maintained for its entire life up to recently, and thse receipts are available, doesn't it provide some insurance that there isn't a major problem? If an MB dealer noted major problems (such as major oil leak or defunct self-levelling suspension) during other service, it would usually be noted on the record, correct?
I've done all kinds of other research on these cars and feel I know almost everything about them but I've never had the opportunity to drive one because we're relatively out of the way up her in Northern Wisconsin.
Thanks in advance for your advice.