Yeah, you're crazy... wild and crazy. Six months from now you'll be sporting that insanely ecstatic grin that's the Portland Winter Bike Commuters' Badge of Honor. You'll be Fit Fantastic Fire Maple Girl. You'll enjoy the Freedom of the Road, and be a mentor to Noobs.
Seriously, you are making a good choice. MonsieurCris is right, the toughest times will be in the dark cold mornings. Don't let that defeat you. There are many others of us out there, and we're even crazier than you!
I would echo all MonsieurCris's advice and add: get good lights, front and rear. And rain riding apparel.
Don't get discouraged if you're sore at first. You'll find yourself getting stronger over time, with more endurance than you ever thought you had. Be patient, listen to your body, but also occasionally challenge yourself.
As for bike shops, I'm partial to Bike Gallery (Hollywood). Their technicians are knowledgeable and friendly. River City is also good. Both shops will help you learn how to fix a flat.
Please post again after you've started riding to work.