I have a 2005 Coachmen Mirada Class A Motorhome and the fuel pump supposedly died. I have been quoted over $2000 to find an after market pump and replace it. This is from a Truck Garage. Supposedly Forest River does make them anymore for my rig.
To start with you need to find a better mechanic. With that said Forest River never made fuel pumps they only make the RV part of your motorhome they use chassis built by Ford Dodge GMC etc to build the motorhome on you need to know who built the chassis to find the fuel pump and any other needed engine parts.