Let's say, hypothetically speaking, that one were to strip the threads off the inside of the crank arm while using a crank arm pull. Would one need to replace the entire crank set or could just the single arm be replaced or possibly rethreaded? Now, let this be a lesson to the person who was in a hurry and not using his/her tools correctly.

I hypothetically stripped the pedal threads off of BOTH crank arms. (Young and foolish I was.) Depending on the make of the crank, you can replace either crank arm, though the left is cheaper, of course.

Loose Screws, at www.loosecsrews.com sell them.

Just heat up the crankarm with a propane torch, the aluminum will expand making the fit to the spindle looser, then you can just tap it with a hammer to pop it off. Wheel pullers work too, try a hardware or automotive supply store