I was in a front end collision in my crx wich totalled the car. I wanted to put the motor in my sedan but where the motor mount threads into the block it cracked off. Not just the bolts cracked but chunks around the block. I assume this means its done for correct? Its just a d15b2, so in a way this forces me to upgrade to something better.

 

If you can post up a pic I can tell you for sure if it's 'done for'. I would think it'll be fine, just take it to a really good aluminum welder and have him weld the broken piece back on or if you don't have it, if he's good he can just remake the missing piece.
My old buddy had an 01 Civic and he burned up the tranny, so he got one from a junk yard with the same frontend collision as you. The top mount on the tranny broke off one of the holes where the studs thread in for the motor mount and we took it to a good local welder and he welded it up better than stock! He even re drilled it and tapped the hole for us. I think it was only 20 or 25 bux. Never broke again. And we were hard on our cars. Lol.