Will a swazall do the trick for cutting a hole for a window and what if I have no practice using it?

Would it work? Yes. But those saws can be difficult to control, especially if one is not used to using one.

Better would be a saber/scroll saw with a long blade. Better still would be to drill a pilot hole, then use shears or a nibbler.

Wires run up inside the walls. The frame inside of the wall is aluminum channel where the windows have the clamping force.

There are more things to consider when whacking a hole in the side of your coach.

I use my roto zip tool and it does a nice job on the skin.

I would not cut any holes in the skin without first removing the inside wall panel to be sure what is there.