It left a sharp edge on both sides but it's covered by my box anyway. YOu should take off the panel on the backside first and assess your situation from there.
Saber saw? Sheesh, I just drilled 6 holes. Took 3/8" bit I think, not sure. One time i didn't get in the center of the weld, so i had to make a 1/2" hole. Much easier than a saber saw though, took about 5 minutes. Left 6 small holes, no deadly mess.
Nope, I drilled through mine, 2002 S10 Ext. It is one layer of thick steel that exit right out between the bed and cab. I drilled at the bottom right corner though... You will have a hell of a time putting back the carpet on the wall if you dont take apart the 3rd door edge (plastic thingie that hold the carpet down)
Hope that Helps,
PS. I woudl water proof and seal anything you put through there becasue it will get wet if you dont.
the back wall is thin as hell 1 sheet of thin metal. to get the jack off i just took a chisel, and chiseled down along where the welds are, the used a welder to close up where it was pop riveted or welded or whatever they did to it