Thanks DTF for the quick response. I called the Benz dealer and they told me there are 4 channels for drainage, 1 for every corner. I'm not sure if they're giving me the right info though. So I ordered the part which I think is just a rubber tubing and cost around $7 each. Anyway, I went to my mechanic and had air blown into the 2 front drains and just hoping the dirt will clear. We can't see the rear drains so I'm just hoping that the 2 front drains will at least help until I find an answer to my problem.
I'm going to check with my body shop and try to find out if there are really 4 drains for the sunroof and if they can replace it. If you or anybody who reads this know any info about my problem please let me know.