Regarding question #1:
http://www.winpcap.org/install/default.htm[
^]. Look for supported platforms. In case you can't find it: The answer is yes!
Regarding question #2: It depends on what you're after. Do you want to only capture the TCP/IP or UDP traffic all should be set and ready to go with WinPCap. If you're interested in the raw 802.11 data you might want to look into
AirPCap[
^]. This is an WinPCap extension that integrates seamlessly with WireShark for instance.
Regarding question #3: Capturing the packet should not be a problem. TCP/IP or UPD use WinPCap. For the IEEE 802.11 data use AirPCap.
Regarding question #4: You will not be able to do this (without quite some pain). What you are attempting is a so called "man in the middle attack" and this is not so easy to do in a WLAN environment.
Best Regards,
-MRB