"Overcharge" is the name of the game. 30 minutes for the filter and 2-3 hours for the fuel pump, IMO.
Here is the DIY link. Only difficult steps are removing the seats (heavy) and tightening the fuel pump o-ring. If you replaced the CPS you can do this too. http://www.benzworld.org/forums/w163...e-install.html
Make sure fuel pump/filter is the underlying problem before you get into this project. Start with the OBD codes if you have a check engine light (CEL) on. On the other hand, fuel filters recommended for replacement every 60k miles as a maintenance. Otherwise it can decrease the lifespan of the pump.