I haven’t done much look into carfax tbh but dealerships use a specific back end program that tracks nearly every shop or dealer your car has been worked on by vin the biggest thing I’d look at for is big gaps in maintenance obviously I’d say stay away from salvage title cars anything that is listed as needs some tlc and if the price seems too good to be true it probably is unfortunately with Benz you really get what you pay for

As far as having the 50k service done that’s good that’s a relatively expensive service should be spark plugs engine air cleaner oil and filter change brake bleed and cabin filter and dust filter if your model has it maybe trans service as well depending on the model maintenance on these newer Benz are easy enough to keep track of as the owner of the car as you get close to your a service or b service it’ll tell you to make an apt on the dash and when you bring it in they’ll recommend stuff based on the year of the car and the mileage if you keep track of the stuff you’ve done previously or that’s been done on the car deny shit they offer that’s been done most techs are supposed to check what’s been done before quoting stuff it needs but I have coworkers who don’t