Mines a Onan, which is now cummins/Onan. Its a 82 PA 454, Genny slides out after the 2 bolts are removed. Someone installed a junction box that you need to get the genny by. Make sure you have a good length on the electric wires that will slide out also. As OP say remove the gas line and you will have to take the muffler off to get the genie tray to completely pull/slide out. Mine only pulls out so far and it stops. I used NO supports.
My issue turned out to be the Choke. It is electric and heats up a coil that warms the carburetor/ butterfly. I replaced it and still had a problem. I took it into a cummins/Onan repair shop and they got it to work, except it still doesn't.
I have to open the panel and hold the choke needle to off to on till she smooth's out, (not even a minute) they told me that's how it works,
I have to disagree, kind of hard to reach the needle from the drivers seat while starting with the dash button!!!! But she runs like a top after it warms up,
Mine has just over 300 hours, not even broke in yet.
Tell us what you find out.