2007 E550 - what is it worth?

[cvgbenzlover]

My other half has found a 2007 E550, black/black with 34K miles P1 & P2, MB certified - the Benz store is asking $39,900. We are thinking $35 - $36K is fair price for the car, what do you all think?

Also they are telling us that we can extend the warranty for 2 more years at $1,800 - has anyone had luck negotiating that down? The dealer is telling us the price is fixed and they can't cut it - I don't believe them! Any real world experience out there with MB Cert extension price negotiations?

Thanks, Mark