QUOTE
run an ethernet cable from the cable modem to a router so the laptop could run wireless
That's the normal way it's done, as far as I know. "Router" in this case I assume to mean a WiFi router, not just an Ethernet one.
However, unless you really need to be mobile with a computer, a straight Ethernet network will be much faster and many times more secure.
Have you considered a refurbished Apple laptop?
Do you use the Universal Access prefs?
Have you considered simply getting a large monitor (needn't be an Apple brand) and a new(er) mini? Especially if you already have another keyboard around.
The mini will be about three times as fast as your DA. Of course, most new Windows laptops would be also. But are you ready to spend the money/time/effort not only with AV software but with the new Windows OS? Not to mention file compatibility issues. I'm sure you think I'm just an Apple shill, but I really wouldn't want to start on a new OS at this point in my life. YMMV. And I don't work for Apple, anyway.
Hopefully, you'll get some Windows specific advice soon. Wishing you the best in your searching no matter what you decide.