confused...access point?

I need a remote receiver to pick up wifi from a long distance ...in other words, i need a "box" that does the exact same thing as my wireless PCI card or USB dongle... only connected to my computer remotely by a long run of CAT5 cable so I can get an antenna on the roof (computer is in the basement, microave coax cable to lossy over those distances) Do i need an ACCESS POINT? Im getting conflicting info on exactly what a access point can do. Can a regular D-link wireless router be set up to receive wireless internet as opposed to broadcasting it to other access points?

Yes you need a AP, the best i can suggest is a outdoor unit that can be a AP or wireless client, antenna is built in and its outdoor rated up to 7 km, try this
Long Range Wireless LAN system---Zigwire
Product Name:ASU-24005g
Product Class:Long Range Wireless LAN system
Features: ASU-24005g 2.4GHz, 802.11g , Fighter Outdoor Long Range WLAN

Details...
Hope this helps, if not email them and they will help you www.zigwire.net