Brian:
It's very easy to remove the lock mechanism IF you can turn the key --
just press the little button on the back and it comes out after you
unbolt everything. You can then examine it and decided what to do --
it may only need cleaning, may be shot. Don't wait -- again, you have
to destroy the locking mechanism to get it out if the key won't turn.
Luther:
The tumbler is MUCH cheaper than the parts you ruin getting a stuck one
out. Buy a new tumbler (yours will come with a new key as well) and
avoid being stuck in a dark parking lot in a bad part of town late at
night!
Peter