Don't worry about it. Networking is one of those things that is not heavily covered. It's assumed that you already know that stuff, but I began not knowing a thing about networking. Now I do, and I think I can answer a few of your problems. NOTE: I don't mean to imply that you know nothing, just basically stating what I went through.
You don't need the EvoX boot disk if you have the X3 bios. Do you have an Xecuter 3, or an earlier chip? If you have the X3, use the bios. Moving on...
I assume the IP address of the XBox is something like 192.168.0.xxx. Change the IP of your computer to 192.168.0.100 (unless that is the 'box IP, at which point use 192.168.0.10, it doesn't matter as long as the first three sets of numbers are the same). Then, open FlashFXP and FTP the XBox at 192.168.000.xxx with the username and password "x3" if you are using the X3 bios or 192.168.000.xxx with username and password "xbox" or whatever you have set it to if you are using EvoX. I think if you are using EvoX, the standard FTP stuff is "xbox."
Did that help? I hope so. Good luck!
- Greg