ok, well the quicker solution would be to buy two routers, one with wireless and one regular, i can persnoally suggest linksys as they have built in abilite to network with/work with their own routers there even deisnged for stacking. i wouldnt suggest going with the G modle as its not a standard (at least not that ive heard) why you get more speed your not likly to see that speed over your internet, just locally, and moving files at 11mbps is fine anway :D windows cant actually handle file bursts much bigger than 40mbps even directly connected (via ethernet cable pc-pc)
i would suggest siwthcing to cable if you can handle it
i think releasitc coverage is about 75-100 feet, and thats in a bubble like fassion i have a small house and i even get decent reception from outside for abit.
also depends on insulation and whats in the way.
setup would be two linksys routers stacked ontop of each other with the wirless as the main. a wireless should be able to handle quite a few computers (10~)(also more than this and P2P over lan slows down anyway)
you then connect the regular router to the main router via a crossover cable, this will give you an aditional 3-4 slots depending on the make.