I don't think you sound stupid -- you have to start somewhere.
It looks like the Miyata listing isn't up there anymore, but if you have questions about the components on any of the other ones and can find out what they are, I'm pretty sure that a lot of people here could tell you if they're good, and also (possibly) whether or not you'll find it more expensive to maintain them than it would be to maintain something newer that might cost a little more up front.
Brake shoes, tires, tubes, cables, and cable housings are all consumable components anyway -- often the ones that come from the manufacturer aren't that great (especially where tubes are concerned) to begin with. They wear out and get replaced over time, sometimes with better stuff, sometimes not. That being said, cables, housings, and brake shoes need to be pretty reliable even in their inexpensive incarnations, since they're largely responsible for safe operation of the bike. Even the cheapest brake shoes need to be able to stop a bike reliably, when correctly installed, or their manufacturers will go broke paying off the resulting lawsuits. Snapped cables could present similar problems; therefore, cables tend to be pretty reliable (some probably do provide crisper shifting than others, but a lot of that has to do with adjustment).
The quality of the drive-train components (derailers, chain rings, cogs, cranks, bottom bracket), the main brake parts (calipers, v-brake system, or what have you), and the frame are the ones to watch, since those are the parts that are expensive to replace -- but unless you're planning to race or do long-distance rides, as long as they work well and get the job done, the bike fits you, and you enjoy riding, just about anything will do, as long as the price being asked is fair.
I think Oxtox's suggestion of identifying a budget first is probably a good idea. If you know how much you want to spend, it's easier to look around and find something that suits that budget. If you're a fan of classic bikes, but you don't know much about them, you could start somewhere like here or bikepedia.com to find out what the OEM specifications and MSRP were for a lot of them, which will help you form a basis for comparison. Determine which models you like, then look them up and see if you can find out how much they originally sold for and what people think of them.
If one specific model interests you, you can also google it and compare the price being asked with what others are selling for. I did this when I bought my road bike recently -- both for the frame (a Specialized Allez Pro) and the components (Shimano 105 groupset -- not the original Ultegra set with the exception of the front derailer, which is original to the bike, but a great set at the price I paid) and came away very satisfied that I was getting a very fair price on a bike that would serve me really well. I absolutely love the bike and think it was worth the time and effort. It's certainly a much nicer bike than I could afford to buy new right now.
Everyone here will say that the most important thing is getting a bike that fits, and they're right. When you're starting out, weight, speed, and all those other details are really unimportant, but if your bike doesn't fit you well, you won't enjoy riding it, and if you don't enjoy riding it, you won't ride. Thus, if for no other reason, I do think hitting the bike shop is a good idea, if only so you can get a sense of what the best fit for you will be.
Good luck!
