Ok, I ordered and received the new part. I got the mower deck assembly
off (which I can tell is going to be a real B$TCH to get back on).

There is a bolt on the top of the mandrel that holds the belt pulley in
place and I assume secures the mandrel into position as well. The
problem is that this bolt is on there REAL tight and the current
mandrel spins when I try to remove it. I can't grab it with enough
leverage, no matter what tool I use, to hold the mandrel in place and
get the bolt off. Any thoughts on a method to keep the thing from
spinning so that i can really put some muscle into the bolt?