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