If I understand you correctly you might want to look into some plugins, I bought one called Xplode for 11 bucks and it works great, there are some free ones also, I think I heard something called Xbreaker might be useful and free. it would be a lot of work to set this up without them. then again if you just want your object to collapse with flat polys (not chunks) then you can start by separating your polys and tossing them into a mograph fracture object.
but like Michael the mega poster said, a closer look at the file / more info would be helpful.