Welcome, Heather! You'll love it here! I started very slowly with running and now I'm hooked. The key, I think, is just to get out there and do it as often as possible, and as comfortably as possible. Don't push yourself to go too fast -- I had trouble with that because I kept thinking I was just way too slow. It's ok to be slow -- I'm still slow, and I probably always will be!! But I can run reasonable distances now and I'm improving every day, and so will you! Check in frequently and tell us about your progress!
Edited to add: As for the bra situation, I still wear two bras when I run. I never wanted to spend much money on a heavy-duty support bra, as my sizes changed pretty frequently (down from a double D to a single D now and still getting smaller). I wear a regular comfortable bra under a sports bra and that has always worked quite well, even when I was quite large in the beginning. Wearing two bras isn't uncomfortable, so I've never had a problem with it. No jiggling, which is good.