Sometimes this happens, .3's and .4's run a bit warm so fluid expansion is noticable, when cold the fill level should be below the bottem line on the stick about 1/4", fully warmed up after 10 or so miles, dead on the top line, just tell them to suck it down to 1/4" below the bottem line on the stick in PARK!.
Clean the underside and it should be fine, providing the vent is not plugged, it shouldn't happen again. After they get the level right (check it before you leave) don't go there again, mistakes happen but, I still dont feel like they were being honest about the trannys internal condition. Most Benz tranny develop shifting issues when they have internal problems and you said prior to going in, you had none.
I remember this tranny shop in Charlotte that would bring in a car for sevice and lo and behold, the fluid is burnt, looks like it broken. Lets do a RCI for $250.00 yadda, yadda, yadda. Tranny fluid is used for hydralic pressure, cooling and lubing, of course it'll be "burnt" after 30k or so, unless it's flat cooked and the pan is full of debris, dont sweat it as long as there are no shifting issues. Some debris, carbon and brass is normal in the pans, ignore that too.
I pulled the pan on my Dodge truck after 30k for service and it had neat little pliles of metal, lots of carbon and funky smelling fluid, still going strong 90k later. My 92 TE got a overhaul after 170k because the front clutchs wore to the point that the apply piston was hitting K2 drum, still was shifting fine. Too many tranny shops want to use "burnt" fluid for a excuse to overhaul a prefectly ok unit, I guess fixing one that is not broke is easier than fixing a broke unit huh?
If you want a second opinion and can fine a excuse to come to Raleigh for a day, come see me, we'll test drive it, drop the pan and check it out. We get $1200 to rebuild .3's and .4's if they need it, hard parts extra. Most dont need it.
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