Whoa -- hold on there! Wrong advice!!!! You really need to siphon out that fluid -- read on:
Andy Kuo wrote: "...As for tranny fluid(or any fluid), it expands when heated, so, it shouldn't be anything to worry about. Just make sure you fill the fluid up to the proper amount when everything's cool...."
That's a really BIG mistake. Your dipstick is CALIBRATED to show the accurate (proper) amount of fluid when the transmission is FULLY WARMED UP. In fact, when the fluid is not warm enough, it will show less than full, and that's perfectly normal -- but you should know that it should NEVER be above the full mark. MB dealerships have charts (and thermocouple probes) to measure fluid temperature and adjust dipstick readings (for levels below full) to determine proper level.
Actually, it sounds (from your description) that someone seriously overfilled the tranny, thinking that the level should be made on cold fluid -- that's very bad! Your leak may even be caused by excessive pressure blowing a seal (but I can't be sure about that).
You should realize that it could take about a 1/2 hour (depending on season, of course) of driving to get the tranny properly warmed up -- I guess your mechanic (certainly not a MB-certified mechanic) didn't know that?
Best thing is to siphon out the excess fluid. Your tranny, and your wallet down the road (if you're tranny isn't already damaged), will thank you.