sunroof

i have 99 ml 430. it has 66000 miles on the clock. i have found a leak in the sun roof. usually this happens when it goes through a car wash with high pressure water. it does not happen when it rains
are there any adjustments or maitenaince that can be done by a do - it yourselfer?
the car is out of warranty. I am usually pretty handy but i do not know where to start.
thanks.