I agree with you man. Knowing you can do things like that is a good feeling. But even though you may not screw up and ruin just a block, what if something goes catastrophically wrong and destroys more than just the block. Then your out way more than the machining cost. I don't know what could happen but as hard as some of these motors are pushed, seems like you should leave it to an "expert."
I thing i would just take it to the machine shop. Just my opinion.