What kind of derailleurs does it have now? Unless you've abused the bike (it doesn't sound like you have) you can probably get by with a new freewheel and chain, moving the shifters if you want to do that, and new brake shoes. I'd try that before installing new brakes, unless there's something wrong with the ones you have. For the shifters you might think about some Suntour barcons (bar-end shifters) - like my avatar. They're pretty foolproof, work well and are easy to reach while keeping your hands on the bars. It might help if you could post a few pictures of your bike. At any rate, we enjoy bike pictures around here.