Hello and welcome to the forums.
There are many ways of accomplishing this, personally I solved this problem by employing an Ethernet over mains power solution using this
; I find that it is almost completely reliable and you can easily stick a 4 port ethernet hub on the other end for all your devices (some of the more expensive versions have a hub built in).
It works by taking your ethernet signal and sending it through your houses power cabling and then receiving that signal at any socket in your house.
There are other options but personally I think this is one of the best.
In answer to your question about your WLAN Card being used as a router then the answer is yes.
You can set it up as an ad hoc network on any version of Windows or if you are running Windows Seven you can use this nice little program called Connectify
which accomplishes the same thing but is much more versatile and easier to manage.
I hope this answers your questions.