You can wait a few weeks if you barely noticed it starting to leak. I'm not sure how long it takes to get fluid into the control module but I'm sure you got some time. I'm pretty sure you need to be losing a lot of transmission fluid and driving for several months to ruin the transmission. I haven't seen that too often. Just don't forget about the leak entirely.
The guy already said he doesn't know much about cars, he's only going by the snippet of info given by the dealer mechanic. If I get a statement from a mechanic that says, "Your electrical plug is leaking and needs to be replaced," my first line of questioning to him would be "Leaking what, electricity? Amps? Where are they all going? Can you just tape it up?"
Seriously, some of you really go that extra mile to make a guy feel welcome!
My whole point is to help Marty understand the potentially SERIOUS nature of this issue. PLEASE NOTE that Marty DID NOT notice the leak. It was brought to his attention by the dealer. Thus, he has no idea how long it has been leaking. THAT IS THE BIGGEST PROBLEM. Of course you are right that if it just started he can wait, but how can you make that assumption?
In my case I was under my car replacing my cats and inspected the adapter/connector/bushing (whatever MB has decided to call it this month). It was clean and dry.
One week later I looked under the car to check something and guess what? A small puddle under the right front corner of the trans pan.
Now of course had I not just carefully inspected it, I wouldn't have driven it past that, because I'd have been in Marty's shoes. He might have been driving it that way for months. So I can't in good conscience tell him he can wait, because I'd feel pretty bad if he drove off blissfully and lost his module or the transmission.
So, Marty, I'm sorry if I offended you in any way, but you have a nice, newer car and I for one do not want to take the chance that you damage it. That's the reason for the strong language.
As has been noticed, any shop that works on MBs can take care of this for you, but if it's not a MB shop you'll have to buy the part and take it to them.
If you're near or over 50,000 miles, I would suggest that you have the fluid and filter changed at the same time. Both items on the same ticket together should be in the $300 range -- depending on your market and the relative greed or hunger of the shop. Dealers are likely to be much more, I've read a couple of threads recently where two guys were charged in the $200 to $250 range just to replace the connector and top up the transmission.
Take care and enjoy the ride,