Good networking guide?? Advice on Setup??

Can anyone recommend a reference site for home networking?
I'm not an advanced user, but not a computer dummy either.
I've got 2 PC's, two Xboxes, and a connected DVD. The 2
PC's connect to the internet via a wireless router. Each PC
is sharing it's internet connection with an XBox via
ethernet. I also have a DVD player that connects to one of
the PC's wirelessly. I've come across 2 situations.

1. I've had trouble connecting the DVD client wirelessly to
the server PC through the router. I'm only able to connect
on a peer to peer, directly to the server PC. Since this PC
also uses it's wireless connection to access the internet; I
have to go to my network props, and switch connections every
time I want to use the DVD. Is it possible for the server
PC to be connected to the internet and the DVD at the same
time?

2. Both Xboxes connect to Live and play fine at the same
time. My roommate and I can send and receive messages to
each other, but can not join in the same game together. Is
this something that might be fixed by changing the NAT
settings?

Thanks,
Robin