Nothing in this world more expensive than not doing required maintenance and abusing a vehicle, which is exactly what you are doing.

Ask your wife if she'd like to buy you a new cylinder head.

Stop driving the car, period, until you identify the problem.

Could be fan, could be rad (assuming your mechanic has done his work properly) rad's are easy, some of the Nissan 4x4 ones fit with some minor hose mods if you can't find a local MB OEM part.

Either way if it is smelling that hot you are guaranteed to be doing irreparable damage to the car...