1 & 2. Wireless Router: costs around 5,500 (DLINK 724P+ or something), Wireless Card: costs around 1,500 each..
3. http://www.sejutronics.net (I had purchased my router from them)
4. Nopes, just get 802.11G enabled router
By setting up a wi-fi network will you be sharing a internet connection ir is it just for sharing network resources across wired & wireless hosts ?
Depending upon that you need wi-fi network adapters for each host,PCI or USB or PCMCIA cards for laptops, a access point for connecting wired & wireless devices together or a wireless router.
All of the above equipment is not needed,it would depend on what you want to achieve.So tell us your requirements & we will be able to tell you more.
Anyways here is add Linksys costs too which I'm buying in the first week of august.