Bent derailure hangers are really tricky. Get yourself a book on bicycle repair and monkey around with it. You can often get a bicycle repair book at your local library if you don't want to make the investment.
Anyway, fill your head with mechanical knowledge and have at it. At this point, you don't have anything to lose but time. If time is too valuable and you don't have the time to mess with it, then bring it in to the shop. Derailures are not impossible to do, but it takes time to learn how to get them on and get them adjusted correctly. In addition to the derailure, you have to be comfortable with chain "breaking" to get the chain apart and thread it through the derailure pulleys.
Then you have to know how to tension the cable.... ayaiyai, it might be more complicated than I thought.
So, in a nutshell, it is do-able if you have the time to do it - kinda technical (about a 7.5 on a scale of 10), but a good learning experience and you really don't have anything to lose at this point.