As far as cutting, as neal stated, get yourself a mini-pipe cutter... Now, as for sweating the joint, this is probably the point where the pro's on here are gonna beat me with a stick... lol But, when I replumbed my shower, I took an old license plate, and a piece of fiberglass insulation, pulled the paper backing off it (leaving nothing but the fiberglass itself) and doubled it over, placed it against the wall, and license plate between the joint and the insulation... I will tell you that while this method (what I like to call 'redneck engineering') did work well, I am not necessarily recommending you do this as it's obviously not something that's made specifically for this, just something to maybe get the gears turning to give you an idea.