Note this a first post. The OP may not be familiar with all the data retrieval capabilities of this forum.
I towed a new empty 2013 25FB International Serenity home to Phoenix from Los Angles up the mountain at Palm Springs with no issues. The weight of the trailer exceeded the 5,000 pound trailer towing capability of my 2007 ML320 CDI diesel. Newer ML models had that pencil whipped to closer to 7,000 pounds. The actual tongue weight of 1,150 pounds put the ML close to the gross weight ratings for both axles with just me in the car. The air suspension kept the car level.
When loaded for camping, tongue weight was1,175 pounds and the front axle was overloaded and the GVW rating of the car was exceeded with just the wife, myself and an air compressor in the ML.
The diesel had more torque than the Mercedes V8 (not the AMG V8 version) and had no problem getting the rig moving with the paddle shift transmission allowing the driver to keep engine RPM where needed. I was in 5th climbing the steepest part of the mountain at 2,150 rpm.
My ML drive line was not as happy when the trailer weighed close to 7,000 pounds camping ready and groaned on even slight inclines.
I would suggest considering the maximum combination weight rating of the ML and be sure that it is not exceeded. Coming down a mountain with a trailer brake failure could be more than the ML brakes can control if the total weight exceeds the cars capacity.
We immediately shifted away from the ML to a ¾ ton Dodge Ram diesel so we could carry two 2,000 watt Honda generators, two gasoline containers, spare propane tank, chairs, tools and a grill etc. To borrow a Post Office saying. "If it fits, we go" without overloading any important weight parameter with our heavier 2014 31' Classic.
The ML is still my daily driver.
WBCCI Life Member 5123, AIR 70341, 4CU, WD9EMC
TV - 2012 Dodge 2500 4x4 Cummins HO, automatic, Centramatics, Kelderman level ride airbag suspension, bed shell
2014 31' Classic model 30 twin beds, 50 amp service, 900 watt solar system, Centramatics, Dill TPMS, disc brakes, 16" tires & wheels