I would stick a set of rods and pistons in it, Key the crank and cam and oil pump,once you get the motor out to see what all went bad see what work needs done to the block.
lb7 cut (and coated, if you so feel inclined) pistons are the popular choice for rebuilds.
Is there anyway to prevent this or keep it from happening?
some people are fine and some people are unlucky like me
Aside from needing pistons, how much other damage is normally done from the cracked slug?
depends.
On what? lol. I was just looking for a rough estimate. I really have no idea but it seems having someone pull the motor, build it, and then putting it back in would be very pricey!