OK, I've flashed the DD-WRT firmware onto the WRT54GS and it wasn't very hard. The site survey works and I can connect to my chosen wifi router.. What I can't do is get the internet to connect wirelessly even though I have three other computers linked through the wifi router.
I'm trying to connect to the Tmobile@home wifi router and can't find some of the settings on that router that DD-WRT seems to want me to change.
Edited to add: The DD-WRT Wiki says I need to set up a static IP addy _under_ the the normal range of the wireless router, my router does not appear able to do that as far as I can tell. I'll try to get screenshots later today.
http://www.t-mobile.com/shop/phones/Cell-Phone-Detail.aspx?cell-phone=T-Mobile-@Home-HiPort-Wireless-Router
I set up my first network well over ten years ago and I still don't really understand this stuff.