With the stem (I'm assuming it's a wedge type here) - if the bold unscrews enough to clear the stem itself you could try giving it a whack with a soft faced hammer to loosen it then, with the wheel fixed in, grab the bars and twist - if it still won't come out then take the bolt all the way out and try again (wedge might be rusted in).
There's a thread somewhere on these boards that covers getting the wedge out.
As for the seatpin, you may have some success by clamping the pin in a vice and using the frame for leverage to get the pin twisting to work it out of the seat tube.
Lots of GT85/WD40/3-in-1 will help too.
If the above doesn't work then more extreme measures may be required!
