Drive the rv up on some blocks to gain some working space. Empty the tank of most of its contents. Using a floor jack with a 2x4 or 2x6 on it to support the tank, unbolt the tank and slowly lower it down.
I tried both metal and plastic fuel line removal tools and neither worked for me. I ended up using a small metal pick to release the tabs on each line.
Once everything is disconnected, removing the actual pump is simple. Make sure the top of the tank is clear of debris. I had a handful of walnut shells on mine from some friendly squirrel.
Having an extra set of hands is always helpful.
Good luck. Let us know how it turns out.