Public hotspot

ok I'm a Newbie, so if this is a stupid question or has been answered before forgive me.

I currently have a D-link wired lan network that Shares my roadrunner cable internet connection. And love it. Costs me 40 a month.

So I have recently purchased a new laptop that has a wirelesss card in it and found that there is a wireless network in my area, so after bs'ing with my neighbor about it, I come to find out that the college serves the area with a public hotspot for free ... OMG so here is my question: I want to cancel my service with rr and hook into this wireless thing, but only have the laptop and one more wireless card 802.11g+ that I bought to put in a desktop. Can I use my router to share the connection to the other hardwired computers in my home, like taking one of the wireless machines are routing it to the others, I tried hooking it in the WAN port and sharing it and an error came up saying that there was already a lan ip. Please let me know if it can be done and what I need to buy and do