What Paul said is true....
but I , as a one man shop, chickened out on taking all that metal out to put in a new gasket...
I cut out all the gasket I could without making it fall out of its hole... and put Black Automotive Silicone sealer into mine....
Stopped the leak completely... cost about $20 total for the two caulking tubes....
What is nice is taking the trunk lid off to work on the windshield.... very light trunk lid... only four bolts.. and nicest thing is that it will sit in place due to the foresight of MB in putting a little tab between the bolts.... very cool....