Wireless Setup Help

Trying to set up a wireless network I have a few questions:

1. Will a Airport Extreme Base Station work if I use it with my mac mini G4 using a 3g broadband card?

2. Will the wireless signal be strong enough to travel down the stairs about 25-30 feet away. And will that be strong if I use the wireless N' adapter for my Xbox 360?

3. How much faster would it be if I did this Mac Mini<Airport Extreme<Cat 5 or 6 Ethernet<Xbox 360

All answers Appreciated.... Except the bad ones.

Please refer to the "sticky" regarding wireless networking at the beginning of the forum.

Also you might want to take a look at this list of wireless FAQs: LINK

Regards.