networking questions:

1. Not really sure about this.
2. Having your iBook on the network shouldn't slow it down to much.
3. I would guess that using the TC instead would be faster.

 

If your Internet speed is faster than 54mbs then it won't be slowed down.

 

If you are in N (b/g compatiable) and connect a G device, your network will drop to G speeds.
also i believe (could be wrong) that N (not compatible) will give you faster speeds than compatible, especially if you use the "wide channels" option, but this uses 5GHz which doesn't go though walls and stuff as well, so your range might suffer.

chances are your internet connection is slower than a G signal, so for web browsing and such you shouldn't see much of a hit.
Your time machine backups and network file transfers are a different story though.

the linksys probably has little to no affect on your network speeds.