I did some reading, and this is what I found:
There is a disc that has to be used to set it up on the Xbox, and the ISO for that disc can be found online relatively easily. I don't know what it falls under, so I won't link it, but just remember when googling to use "original xbox", otherwise all of your results will be about the 360 (and even then half of your results will be about the 360). Besides that though, the disc can not run the set up on a modded dash. It basically has to detect a stock dash in order to install it, and that means you basically have to disable your mod in order to run the network installation. This alone makes it not terribly worth it, imo, and I don't even know how you would disable a chip mod like that. Otherwise, after that, you can re-mod and the network stuff keeps working.
A note about the adapter: it is WEP only, so if you have any kind of modern security setting on your router, this won't do jack for you.