If you're not ready to rock the spandex look, big thumbs-up from me for Mt. Borah underliners -- cycling shorts designed to be worn under regular shorts.

My best advice would be to not expect too much as you start out. I work in a bakery, and it's a VERY physical job, so I thought I was in okay shape, even though I am overweight. I used to cycle A LOT...but that was 20 years ago. When I started up again this summer, I literally couldn't make it around the block -- I thought I was gonna die! Just the sight of a hill practically made me cry. I got really, really discouraged (somewhere on TE is my "poor me" thread). But I stuck with it, in large part due to the encouragement and advice I got here on TE.

Now I commute to work almost every day (distance-wise, it's fairly puny, but there are a couple of MAJOR hills), and try to get in a nice 10-mile ride on the weekend. Every day gets a little easier, which serves to motivate me even more.

Good luck!