Disney Princess registration

I did some googling today and found that registration for the 2013 Disney Princess 1/2 Marathon starts July 10, so I have tons of time to figure myself out as a runner. It's about 3 weeks after my beginner women runner group finishes, and I'll probably end up doing another one of those groups for a longer-distance race if they have them for the fall. There's a winter half marathon one but it starts in January and finishes in May.

I'm finding I have left knee pain and right shin pain. Anyone have any suggestions on how to stop those? My mom has a knee brace she's going to lend me, so maybe that'll help me out. I was noticing on Saturday that my issue wasn't with my lungs and being out of breath; it was my legs hurting. I'm 27 - should I really have knee issues now??

I'm looking into replacing my bike. I had a Trek hybrid bike that I loved that got stolen in Denver last year. It would be good for cross training and also just because I really like to ride my bike. The DC area has some nice bike paths. I went to Revolution Cycle in Rockville yesterday and found a bike I loved, which turned out to be the newer version of the bike I had that was stolen. Hey, at least I'm consistent! ;)