How to clean top of gas tank and fuel pump replacement

[Wolff]

Hello everybody,
The fuel pump has quit in my 200. I notice that there is a lot of fine red grit on the top of the tank all over the pump and hoses etc. Apparently my wife did a bit of rallying on her last trip to the desert. At least the pump didn't die on the trip, it died in the driveway.

I don't want any of that dirt to get in the tank when I pull the pump. Should I just wash it off with water? (Will the water just run out under the car, or will it get trapped in some vital area?) Any ideas how to clean it?

How does one release the retainer ring on the pump? Any other tricks I need to know to change the pump?
TIA,
Wolff