I like KSH's idea of starting with a 10 mi./ 1 mi. I think its a good idea to start easy so you get the hang of it without feeling like you're being punished. For me, if I have a bad experience doing something, I'm less than eager to go out and try it again (I guess that makes me sound wimpy, but really, this is supposed to be fun, don't turn it into a torture session!) A good goal to have in training is to generally finish feeling like you could have done more (exceptions maybe being speed/interval work, and actual races).

Good luck! Bricks are fun!