I would pull the tranny and replace the front seal myself and I do have it on the "to do" list for my 300D. I am having to add a little fluid once/week. I put some tranny seal stop leak in it during one of the fluid changes about 6-8 months ago and that did slow it down a little but it needs a new seal. Make sure you get the car high enough to roll the tranny out from under it or get a tranny jack that is low profile. You could probably pull the torque converter and change the seal under the car but it will be more of a pain in the butt. Check your flex disc while you have it out. When putting everything back together make sure you keep your friend over until you get the exhaust/muffler back in place. You may even want to consider replacing the engine rear main seal while the tranny is out. Take your time and you will be fine. It took me three 6 hour days to replace the rear main seal on my E320 but I was working by myself. Make sure you get the torque converter "latched" in during the reassembly.