"I guess I should have known that the dealer was incompetent when they had to ask me how to open the keys..."

BigT - Don't know who your dealer is, but if they couldn't find the V/C leak and didn't know how to operate your key, chances are that they don't have a certified, factory trained X-Fire tech, and probably don't have the special tools to properly repair you car.

You may want to avoid the inevitable, upcoming aggravation by finding a new dealer now, up to and including a MB dealer or independent import car service center.