I have found Urgon's part, but now cannot escape area. Do i need to kill the ice guardian (how?), or can i move on some other way?

You have to kill the Ice Monster, and it ain't easy. Check out page 3 of this forum, near the bottom; some posts there that explain what needs to be done. Still, its really a strategy you have to come up with to kill it off; I don't think anyone can explain how it needs to be done. Took me quite a few reloads of my savegame to get the job done, but not without substantial health damage. Good luck.