I think this is a basic task, but I don't know the easiest way to accomplish it... I just want to cap off hot/cold copper supplies, and remove (or rotate and cap?) the cast iron T joint on the soil stack - and have everything behind the drywall when I'm done.. How should I do this? Especially the soil stack - I tried Googling and couldn't find exactly this (seemingly common/simple) situation.

Some pictures:
http://i285.photobucket.com/albums/ll70/yumbrad/th_sink788.jpg (http://s285.photobucket.com/albums/ll70/yumbrad/?action=view&current=sink788.jpg) http://i285.photobucket.com/albums/ll70/yumbrad/th_sink789.jpg (http://s285.photobucket.com/albums/ll70/yumbrad/?action=view&current=sink789.jpg) http://i285.photobucket.com/albums/ll70/yumbrad/th_sink791.jpg (http://s285.photobucket.com/albums/ll70/yumbrad/?action=view&current=sink791.jpg) http://i285.photobucket.com/albums/ll70/yumbrad/th_sink790.jpg (http://s285.photobucket.com/albums/ll70/yumbrad/?action=view&current=sink790.jpg)

The horizontal pipe going into the cast tee can be unscrewed with a pipe wrench, plug with cast or PVC plug. The copper lines can be cut after you turn off the water and bleed the pipes of pressure. Solder two caps and you are done. Soldering requires both pieces to be cleaned with plumbers tape or emery cloth, fluxed and soldered

Thank you! A clarification - the horizontal pipe seems to be "glued" into the cast somehow, and the cast tee protrudes beyond where the drywall will go. Can I bang it with a hammer (saw this advice somewhere) to get it out, then turn the tee 90 degrees before I use a "plug"? Also, I don't seem to have a "rate this answer" button, maybe because I'm new?

Yep, you can't rate folks until you do 5 or 10 posts. You can try to rotate the teee but it likely will not work. As you rotate you make one of the other connections loosen and the other gets tighter, probably neither is good. You could just cut of both galvanized pipes and the spice a section of pipe in with Fernco couplers top and bottom. Do you know if this is a wet vent or a drain, anything above it draining?

The sink was the only thing on this section of stack pipe. There's quite a bit of threads above and below the tee, will it still get tighter/looser such that turning it 90deg won't work?