Vehicle Video survallience

This is my first post (just joined), So I thought i'd ask a good question:
I own a Semi truck. I have 2 video cams (RCA connections), an indash monitor, a notebook.
Now what I need to do is have a way to get the video into my Dell Insprion 1100 I have USB in , I use a PC card Wi-fi, and reg cat 5 network adapter. I plan on adding 2 more cams, so I will need 4 RCA in convert to USB and record software. I will get an ext HDD for storage, I figure it will take around 3 gig a day to record.
if you are curious about what it looks like here is the link
http://www.9thweb.us/tech/
Any help would be greatly appreciated