If it's trans fluid leaking it's probably the front transmission seal, a common leakage point. Either that, or the pan gasket is leaking. Be sure to check that, could just be the pan gasket. If so, you're out for just the cost of a transmission service kit & new fluid and the associated labor.

If it's the front seal, it's inexpensive depending on how you look at it. The replacement seal probably costs $10. Hiring a qualified independent Mercedes mechanic to install it could be as much as $1k depending on who you get to do the work and what the shop rate is.

For a dealer, huge money. Huge. Bigger money than the independent mechanic would charge. They have to keep the lights on somehow.

Determine for yourself where the leak is coming from.

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'02 BMW 325i
'85 300D 450k
'93 190E 2.6 170k(killed by tree)
'08 Ducati Hypermotard 1100S 6k
'06 Ducati S2R800 14k(sold)