Is it worth the time and money to replace a broken timing belt myself.

On the way to work today on the frontage road I was down shifting from 3rd to 2nd and I heard a loud clunk followed by the engine stopping. I popped the hood and see that there is a piece of a broken plastic sproket poking out the passenger side of the timing belt cover. I am a man of very little means these days and was wondering if it is worth rolling the dice and putting a couple hundred into the timing belt, sprokets and such. Or am I just dreaming that the valves aren't cashed and need to be sent out?