I haven't tested with that motherboard, but it would be minimal work. The nView software is built in to the nVidia drivers, if I recall correctly. Basically, you just hook up the second monitor and configure it via the Display Properties. To be honest, I haven't really thought about it since December, when I set this up. Though I set it up with a PCI card in addition to the AGP in my workstation (on the PC, that is - on the Mac, it all goes through one video card).
The only problem I can see you running in to is that the onboard video on T-$'s motherboard is AGP, as is your GF4Ti4200, and there may be a conflict there.
A cheaper and fool-proof route is probably this one:
http://www.newegg.com/app/viewproduc...on=geforce+pci (I got the Chaintech one with 64MB of RAM)
By the way, dual displays don't have to be the same type of monitor running at the same resolution. I convinced Giles to hook up dual displays on his PC and his iBook (though he uses the same monitor and toggles between the two computers), and he was running a 17" and a 19" for a while there, both at different resolutions. Windows does a pretty good job with it, and nVidia's software makes it a snap.