My best advice is to buy from a MB dealer as opposed to private sale or BHPH lot.
Thought being that even though it’s not going to be CPO at that age, at least you have a chance that it was a trade in from a loyal customer who always maintained it.
Here is a search I use to find MBs at dealers. Edit the string to put your zip code instead of mine.
https://www.mbusa.com/mercedes/cpo/inventory/zip-29229/class-E:SDN,GLK:SUV,M:SUV/fueltype-D
At the top check the box that says ‘Include all pre-owned’
There is a history document called a VMI (Vehicle Master Inquiry) that is an internal dealer only document. If you get serious about buying one ask the sales guy to go to service department and print it out for you so you have the history. This info comes from the MB servers when the repair orders are loaded at the dealerships, so it will only have MB dealer service records. Later models store all the service history in the on board computer, but you have to have a proprietary MB laptop and interface box to read it.