All you really need is a bike with braze-ons to mount a rear rack, dropped bars, and a bike that's the right size. All the rest of it doesn't matter much, in spite of all the discussion that goes on about this and that. The very fact that there is discussion means that most of it is a matter of personal preference, which you don't have and don't need to have. All you need to do is ride.

I wouldn't think a used bike would be too hard to find. I see a whole pile of them right around me. Prices run from $350-$700. You don't need brifters at all. Bar-end or downtube shifters are fine. Too bad you don't know much about bikes or you could buy a Nashbar touring frame for $100 and build it up with cheap Nashbar parts and used stuff you could scrounge from a LBS.

All that said, the Windsor sure looks like that bike. You need to know what size is all. If you've been bugging your LBS then you must already know what size? If not, get in there and get them to size you. You can pay them back by buying stuff that doesn't come on the bike: bottles, pump, pedals, shoes, probably a different length stem, possibly a different saddle, etc.

The important thing is to get the frigging bike and start riding it, like now. Don't even think about a different saddle until you have a few hundred miles on the one that comes with the bike. It doesn't even matter how the bike rides. It sure as heck won't ride the same once you load it up. However it rides, you'll get used to it pronto.