Dave, I think you would be best advised to have a professional do the repairs for you here.
Garage doors can be complicated and is best repaired by a professional who knows the ins and out's of the door mechanics. Could be expensive but can also save you from getting hurt.
If your handy and have a second set of hands to help you, You can purchase the track and parts needed at some lumber yards or simply go to companies that sell these doors and buy the parts.
Garage doors can be heavy and depending on the type of spring system you have you may want to send this repair out to those who do this every day. But if your willing you can do this, just be sure you support the door from closing down when you open it to do the repairs and that it does not fall when you remove the damaged track.
Just be careful if you decide to go the diy route and be careful of the spring system.
Looks like we're getting quite a few garage door posts. I really recommend going the professional route. Sure, it costs more but the risk of injury is high and really not worth it if you have to fiddle with the springs.