I like to pop the bleeder, so I am not pushing old brake fluid back up the lines (not to mention that if you topped the MC up since the last pad replacement, it will likely overflow).
I have done it like James does and that works (best to put a piece of wood behind the caliper to protect it, like I am sure he does). And now I use the tool Paul mentioned, which works very nice. They are like 5 bucks, so why not get one.
Jason is so spot on - if the caliper is that hung up, I would not want to reuse it. It will likely drag, bind and eventually seize (after a hard stop).
On old calipers, I have removed the dust boot and cleaned out the end of the bore (lost of brake dust gets in there). Rebuilding calipers is no biggie, but with as cheap as reman'd units are, there is no point IMHO (on bikes, I rebuild since reman'd ones are not a real option).
Whatever you do, do it right. Otherwise it will be unsafe and end up causing issues down the line (warping your new rotors, etc and cost you more money).
Good luck.