setting up wireless network

I have set up the wireless adapter on my Dell Dimension 8200 XP computer w sp3. I had purchased a Tenda wireless router about 8 months ago but I just took one look at the documentation and gave up as it was overwhelming. Their tech support is in China so that's a dead end for support. The router was a 150 mbps router that seems slow anyway in today's standards and looking at an old Belkin G router, I noticed that I could follow the documentation as it was very clear so I plan to go out tomorrow and buy a decent Belkin router with at least 300 mbps and a USB port so I can easily transfer my network settings.

Now all this is Greek to me and I'm all set to screw it up. I want to bring this XP computer upstairs once the network is set up and leave the Dell XLS Vista machine (which I plan to upgrade to Windows 7) downstairs in this room connected to the cable modem, I'll probably leave the xls machine wired.. I also have a HP All-in-One I would like to connect to the XLS computer.

So my questions are:

* Do I have to set up the wireless router before I create a network on the XP computer or vice versa?
* If I set up a wireless network for both computers, will it work if I leave one wired?
* Can I connect the All in One as wireless even if the XLS computer is wired (assuming I have previously added this computer to the wireless network)?
*I noticed another network on the wireless adapter, probably a neighbor's. If I change the channel on the wireless router, do I have to do something about changing channels on the wireless adapter, printer and computers in the network?

Thanks,

Mark