What do I need for 3 PCs and internet sharing?

We have 3 PCs in a big house (3 floors) each PC with a individual user. Two of the PCs are desktops and one is a laptop. The laptop guy has a Linksys 80121.g (or whatever) PCMCIA card already. The PCs are a mix of XP and Win98.

What do we need to get a wirelesss internet connection going around the house? Is it:-

1. Wireless modem router "G" standard
2. 2 x Wireless reception cards for the 2 desktop PCs

Will any brand do, or should I got for the well known makes such as Netgear, Linksys, 3com etc? Is there any preferable brand?

Does the hardware come with instructions on how to setup the software in Windows? Will there be problems with 98/XP combos?

What is Super G and is it worth getting?

Are "G" speeds likely to drop if the router is far away from the other PCs and has to go through walls etc?

I am happy to have my PC wired (rather than wireless) if this improve speeds.

I also have a spare ADSL modem - would it be a good idea to use this or is it better to get a modem/router given that I (or one of the others) may leave the house in future as it is a rented/shared house?

Also, we want high speed so that if everyone is logged on 24/7, the speeds don't drop - it is likely that 2 of us will be P2Ping. We are planning on a 2mbit DSL service from NDO. Any potential problems?

Thanks