Hi, I don't know what the market is like in your part of the world so can't advise you on how much you should be spending to get a reasonable car.
I have owned an Ml270 Cdi (5 cylinder diesel) in the past. It was quiet and comfortable inside. The engine was good and no transmission faults although I sold the car before it got to 300,000 miles.
I used it on some reasonably tough terrain and it was fine. Even with wheels in the air! Its a case of not throwing a lot off money at a car modifying it but learning to drive what you have.
Off road competence is lower than a Defender but better than many Japanese 4x4's including the Mitsubishi Montero/shogun
The complaint I had with it was body corrosion, the wheel arches and doors especially. Maybe due to the English climate! as plenty of 5 year old trucks get very rusty here.
I enjoyed mine.
Hope this helps.