Networking challenges

We have three computers and a printer that connect to a home network via a cable modem connection through Cablevision.

Machines:
iMac--purchased in 1997, CD drive doesn't work, on it's last legs. It's the only machine that prints, however.
iBook--purchased in March 2002, 802.11b
iBook-purchased in Dec 2002, 802.11b
HP Laserwriter, connects via Ethernet
Netgear 4 port wireless router 802.11b
Airport Express 802.11b/g, WDS

Problems:
The house is 20x60, with several rooms that need to be connected.
1. Laptops can't print through the network, only via the iMac.
2. Jessica's computer is mainly located in her office in the dining room, which has bad connectivity to the wireless network. As well, there is a lot of interference from adjoining wireless networks.
3. It is desirable to play music through the living room speakers. This could be done with the Airport Express.

Solutions:
1. Upgrade the iMac as soon as funds are available.
2. Run Ethernet cable from the living room to the study via the basement.
3. Run Ethernet cable from the dining room to the study.

Cost:
1. Need at least 2 50 foot ethernet cables. Cheapest online price is $25 for both.
2. Need drill bit that's large enough to make a hole for the Ethernet cables. $3-5

Outstanding questions:
1. Is there any way to minimize the holes?
2. Once the ceiling is closed, will this present a problem rerouting the wires later?
3. Will I be able to control iTunes from the living room even if I can't connect to the main network?
4. Should I purchase different networking equipment, say, like an Airport Extreme?
5. Does the Airport Express really support WDS?
6. What if we setup VOIP? Will we have to use the Cablevision setup?