If it is stuck, get some pb blaster http://www.pbblaster.com/store/moreinfo.cfm?Product_ID=1 at a local auto parts store, spray that on, then put a pipe on the end of your wrench for more leverage and break it loose. Repeat this process if it still won't come loose and give the pb blaster plenty of time to penetrate. Remember that the threads are reversed on the left (righty loosy, lefty tighty): http://www.parktool.com/repair/readhowto.asp?id=83
AND remember to double check the left and right if your bike is upside down and if you are coming at it from the inside instead of the oustide, it'll be reversed. Also, I believe that a propane torch can be used to expand it. Chk out www.mtbr.com forums for stuck pedal.
If it is stripped like you say, http://www.instructables.com/id/E9J9S19AF7EP28723J/ - read thru the comments. Maybe just take it to the bike shop or autoshop would be best and see if you can get them to guarantee the crank if they break it. Oh, that reminds me, if the allen wrench (inside) is stripped, get the tool for the outside or vise versa.