Robyn,
Speedy Jim's got ya covered. He's got all the right answers, before you even ask the questions. Once you dig it up, replacing it is really pretty easy. The hardest part, will be cutting the old pipe out and if it IS orangeberg, then that will be easy, with the use of a saws-all, or even a regular handsaw.
The fernco couplings he's talking about are very easy to use. I didn't look at the link he provided, but they are a rubber gasket, covered usually in a stainless steel jacket. The rubber gasket fits over each pipe end (old and new on one side and then new and old on the other). You can slide the stainless steel jacket off to the side of the pipe, as you are working with the gasket and once the gasket is in place, place the jacket back over the gasket. With a small amount of mechanical savy, you can do this on your own.
I wish I was around more this weekend, to monitor your progress (posts), so I could offer some help. But Jim seems to be offering you as good (or better) advice than I can.
My only advice, is to remember that this will be a messy project. From the digging, all the way through messing around with that old sewer pipe. It's never much fun. But I really think you can do it. Be especially careful, when you cut the old pipe. There MAY be a very slight pressure behind that clog, just becuase there is water in the pipe, and once you cut through, a very small amount may squirt at you (at worst) and will probably run in the hole you are digging. Preapre yourself, to deal with that. And prepare to eat your french fries with a fork, the next few days :-)
But again, once you dig it open, it's a fairly straight forward repair. I wish I was in your area...I'd glady help for the price of a 12 pak...
Good luck...and let us know how you are coming.