Thank you all for you invaluable advice. I learned so much from this thread!
I would have liked to go local as I'm a huge supporter of the little mom & pop store, but sadly the two bike shops around here are outrageously priced (at least for my current budget). I can see myself investing in a better bike in the future, but as Colleen mentioned, I wanted to see if I can even sustain riding again before I lay out serious bank for the purchase. (As it is, I spent almost $100 over what I planned, what with a different seat to accommodate my giant ***, a helmet, pump, etc.)
We visited several big box stores, and I have to say I was less than impressed with the selection at a few of them. It KILLED us to go to Walmart...I can't even express in words how much I detest everything that they represent...but they had tons of bikes and I found one that seems to suit me and my needs. (And it's a Schwinn -- I had Schwinns growing up, and always had good luck with them so...fingers crossed.)
It was so weird even sitting on a bike again. It's been literally 20 years or so, and dude. I don't remember it hurting my crotch that much!

I think there's just so much more of me now that everything is distributed differently. Hopefully the new seat will help out in that department, as it's a bit differently shaped and MUCH cushier. And man, I looked like a dork trying to hop on and off a bunch of different bikes in the store. Pure hilarity. Even I was laughing at me.
Right now my boyfriend's in the garage adjusting the handlebars, inflating the tires, and changing out the seat. When he's done and it's all customized for me, I will proceed to try to make it down my driveway without winding up with roadburn. Oy vey.
Thanks again for all your wonderful advice. Will let you know how it goes!