Just to add my experience of W164 ML ownership..
Had mine 3 years now and (touch wood) it has been the most rewarding and reliable car I've ever owned.
I do all my own work, but will reserve the right to send it to an Indy if it needs specialist tools I don't have , or just because I don't fancy getting dirty that day..
The only big expense I've had is a pair of
rear shocks (or more correctly, dampers) (about £50 each) which probably didn't need changing, but I'm picky about handling. I'll be doing the fronts too when the weather improves (about £130 each). Other than a couple of
Parking sensors (£10 on ebay) I've had nothing "go wrong" otherwise.
Oil changes take about 20 minutes with a motorised pump through the dipstick, and I do them twice a year. Approved oil & filter are about £60.
I get an average of 27mpg on mixed town (London suburb) and 25 mile commuting. Pretty astounding for a big old bus, but if you were doing ONLY town driving, expect nearer 22-24.
The performance is very good for a heavy car, though the excellent aerodynamics help a lot on motorways where you should see 33-ish if not straying too much above the the legal limit. A Brabus tuning box improve performance significantly (about a second off the 0-60) without affecting MPG hardly at all.
What I don't like is the ride over our third-world roads, avoid large-diameter wheels if you want to keep your spine into your old-age, and the body structure intact. Alternatively, only go for the air-suspension, but bear in mind the increased complexity.
The fake leather is hard wearing
(check for cracks on the drivers boulsters) but the Alcantara (fake suede) they normally come with, I find difficult to keep clean.
When evaluating a potential ML, check for oil leaks at the engine/gearbox interface, and if there's any, walk away. It could be something trivial, but also could be the
oil cooler seal leak which will be expensive in labour hours to fix. There's an undertray covering the engine and gearbox, so check if it looks suspiciously clean.
Obviously, also check if the electrical bits work, especially aircon, cruise, mirrors, power seats, infotainment and tailgate lock. Any of these can be expensive to fix.
I agree the W164 with all the bells and whistles would be a good choice, but if your budget will stretch to a W166 (and you can live with the styling) it should be more future-proof and more thoroughly developed.
"Servicing" is pretty unspecific term, what it means is "an oil change and a bit of a look-round". Bear that in mind the next time you pay hundreds. "Servicing" is the original cash-cow.