I'll try to help.
1) Si.
2) Yeah. I doubt the DS is gonna affect speed much. When I'm downloading huge files on my comp I get complaints that the other comp goes super slow.
3) Hmm. Well read and do what it says. You'll do some configuring through your browser as well as some stuff with the network wizard. I would just follow the instructions. Was pretty easy if I remember correctly. For that router's setup its probably:
http://192.168.1.1 Go to
advanced and go to
fowarding and you can select what ports different programs can use. The last digits of the IP address can be found by typing
ipconfig in the command prompt. I dunno how the DS is configured yet but for my wireless comp I needed to set the ports to use bittorrent. Can also set the WEP key through the main setup page which I believe will need to do with the DS.