The fiscal cost of war is supposed to be offset by the spoils, but that has never resolved any national financial troubles such as the debt or deficit. By nature, we always consume more than we reap.
The humanitarian cost of war almost always seems to end up hurting the 'aiding' nations' reputations. I'm sure you'll have some people jump on that, but most of the middle east (including Libya) hates and will continue to hate Western powers even after we supply aid.
Regarding Canadian political parties:
Green party doesn't appear to take a stance on war.
NDP oppose war.
Liberals appear to oppose unreasonable wars.
Conservatives' stance on war is entirely dependent on the U.S. stance, so if the U.S. goes in, then we go in.