You most likely wont be able to instal a triple without a new bottom bracket because a triple wont fit on the one you have, since it's fit for a double. That's the best thing I can give you right now without knowing a damn thing about your bike.
What ind of inclines are you talking about that you can't deal with on a double? I mean I know there are some pretty brutal hills around my way that suck on a double but it's nothing I can't power through (with a little bit of training at least: intervals, trainer, etc).
Maybe I just sound like a jackass because I'm kind of drunk.
Edit* Oh the toe clips might not be helping as much as clipless pedals as far as helping you up those hills. Might be a cheaper investment than a new crank...