I would put down a £500 deposit and get it fully inspected by a dealer, get it wrong and I bet a £10k bill would not be unheard of. They will find something and that's just a bargaining chip.

I would also scour the net and merc forums.

I bought an E55 AMG and it had a service pack that had just expired, it still cost me £4K to put right and that was with a mate in the business