First problem........the muffler

I have a 1989 300E in which I noticed the muffler starting to get louder. As I checked nder the car, I noticed a hole about the size of a quarter on the bottom side of the muffler.

My question is if there is a patch of some sort that could be used to seal that hole?

Second question..........where is the fuel filter located on this vehicle? I believe some have the filter in the tank and some are external

Thanks for your time......

Rocco