Like I said, i'm a novice at circuit design, and I've fried too many transistors to help! I understand vaguely what the H-Bridge Circuit entails, but I still need help working through the discrete components!
Ultimately, at your level, you are likely to burn thru more components, and money to boot. Unless your goal is to understand discrete component h-bridge design, and money isn't an object while you learn, cut your losses now, and buy an h-bridge.
Pololu (http://www.pololu.com/) has a decent selection, although the one you would probably want:
...is currently out of stock, and more won't be available until February at the earliest (according to the site).
There are plenty of other vendors of h-bridges, so do some googling until you find one for your budget and needs...
If you're intent on building your own, you could probably use this design:
But substitute transistors in a TO-3 case (with appropriate heatsinks as needed) instead of the smaller TO-220 package; a good common complementary pair would be the 2N3055 (NPN)/ MJ2955 (PNP) for this. You will need to include the diodes, by the way. Be sure to use optocouplers for switching the power transistors (4n25/26 would be OK).
You could probably do a MOSFET h-bridge, but in order to do it right you need to either use complementary pairs (and P-types can get expensive), or you can use an all n-type bridge, but then you have to implement a charge-pump on the top end to get it to work properly.