Very Confusing Network Setup

Hello, I am trying to set up a second isolated network upstairs that does not have an internet connection. However, I want to be able to have it use one of it's connected computers that has wireless to allow other computers on that router to use the internet off the wireless computer. The wireless computer connects to the router downstairs that hooks up to the modem and off to the internet.

I was wondering, how will I go about sharing my wireless computer's internet with all clients on the router upstairs? It seems like an easy thing to do, but I still haven't figured it out.

Here is a horrible picture i made up in Photoshop describing how my network is set up:
http://img156.imageshack.us/img156/2871/networkbo3.jpg

Thanks for the help, I actually found this out before reading your post, lol.

I also had to change the second router's IP to 192.168.0.2 however, because WinXP wanted to make my LAN IP 192.168.0.1 in order to share the connection. I doubt that'll create any problems, though, since it's working fine. I was able to leave the DHCP server enabled on the router, so that if I want to connect any other computers they won't need to assign their own IPs. I also set the DHCP for the internet side to 192.168.0.1, which is my computer with the wireless, so all the other computers on the second router was able to connect to the internet through the wireless computer's shared connection.

I'm glad it's all worked out now, because I hate doing ad-hoc connections with two computers via ethernet, lol.

Also, is there any difference between sharing a connection with a different one and making a network bridge between the two?