All you need is a wireless router. Most of them will come with 3-4 wired ports that you would be able to hook your desktop up to.
You will most likely only notice the difference if you are transfering large files between computers on the network because your local speed will still be faster than your DSL speed for either of them.
If there is not that much of a price difference I would go ahead and get the wireless G (54g) becuase everybody seems to be moving away from that other modes right now and with 802.11g you can use 802.11b equipment with it.
If you have cordless phones check when you first get your wireless stuff and make sure they dont cause a problem if your phones are running at 2.4 Ghz.
Aviod Belkin wireless routers for right now. I have had good luck with D-link and Linksys products but I am sure other people have other brands they like.
