I have had a transmission leak for the past 7 years on my 87 300E at the main seal. Replacement requires removal of the tranny, so it is obviously quite expensive. My dealership actually recommended to NOT replace this seal, because the leak is fairly minor and has never worsened. Remember, this leak has been around 7 years, and my car has never had a trans problem and it now has 170,000 miles on it and she still shifts perfectly as long as I keep her filled with fluid. It only takes me checking the fluid once a month and adding a few ounces. I don't know how severe your leaks are, but if they are not very severe, I would not worry about fixing it and simply keep a watch on it.