Probably not. At $200-400 a piece, a lot of us will ride on a bent radiator before replacing it. If enough of the core is collapsed, it could cause overheating problems, but the radiators usually pop before they get that bent.
Depends on how bad. The radiator is made up of a number of cooling columns, all in parallel. If the bend puts a kink in one of the columns it will prevent or at least restrict the water flow through it. The loss of one or two might not be a problem. The loss of three or four might not be a problem except on the hottest of days. The more you have lost, however, the less margin you have.
Like 76 said, many people are riding around with some pretty good dents in the radiator. I would recommend that you pay close attention for the next few rides for any sign of overheating. If you ever puke water after a really hard ride then you should replace that radiator ASAP.
thanks for the info. how do you post pics i want to post pictures of it on her to see if you guys think ill need a new one or not. the bike is unridable at the moment or i would go ride it and see how it preforms.