Many of us 107 owners have had to drain the tank for various reasons.

First thing I would do, is suck as much fuel out as you can through the filler pipe. Syphon or cheap hand pump. Then clamp the hose from the tank to pump suction closed before disconnecting near pump suction. Put a container under car and drain what is left into that. Better than passing potentially dirty fuel through pumps. Once empty, it might be worthwhile removing the level sensor and taking a look inside the tank. There is a swirl pot in there with a filter screen inside it that installs from exterior. If it looks clean, you may get away with filling with fresh fuel. Best to install new fuel filter after pump first

I have an earlier car, so can't advise about disconnecting after pumps and using them. You might try posting on the Benzworld R/C107 forum. Many more 560SL owners there that can help with your recommissioning.

__________________
Graham
85 300D,72 350SL, 98 E320, Outback 2.5