Onan generator problem

Okay, so my fuel pump filter were original on my Onan 4000 in my class C with 500 hours it so I took it to the only place I could find in the Oklahoma City area and they charged me nearly $900 to replace the fuel pump, filter, an air filter, and a spark plug then load test it. My only problem I was having is that if I parked the RV nose higher than the back, the pump would not pump up enough fuel, but ran fine though loud with central air on. That seems absurd, but their labor rate was $145 per hour. There is a youtube video for how to do it, but at 72 I don't see or work well in dark places where the pump is located or I would have done it myself, but never envisioned a cost like that for an electric fuel pump and a couple of filters.