You are on the right track. You should go with 802.11n draft wireless cards and a matching router if you have the money for it. Otherwise 802.11g will work; the difference is how fast the wireless connections can go. 802.11n can go up to 270Mbps and 802.11g can go up to 54Mbps which is a huge difference.
For two desktop PC’s you will need wireless PCI cards. Both the cards and the wireless router can be found at most electronics stores like Fry’s. You can check out Pricewatch for good deals.
Great Q&A, there are also wireless USB dongles that you can get as well. I would suggest the PCI cards though for a permanent install.