im really lost and i NEED HELP!

alright i bought a linksys wireless B network kit and wanted to connect my computer and my laptop together. Thing was that my dell dimension 4400 doesnt have an ethernet slot. I'm really close to buying one and installing it. If i install it, does anyone know how to remove the tower case? when i install it, ill be using one of the slots under the dial-up modem, and i suppose it should slip right in. When i turn on my computer, what should i look out for? would there be any errors? IM REALLY LOST! How would the operating system recognize the ethernet peripheral. If anyone has any idea, email me at Saybakgung@aol.com or post it up here. I need to get this running by the 31st of august.