To the best of my knowledge you can use whichever modem you wish with which ever ISP you wish..apart from if you are using NTL. You can connect your PC to the modem using USB and your family using Ethernet. You won't need crossover cable to share the connection as the router function will alllow all PC's connected to it to access the net.
Although reading the spec iot states that only 2 PC's can share the internet connection at any one time.
It should be a breeze to set up..pop the CD in and follow the wizard instrcutions.
If you have not already purchased it I would strongly recommend a wireless set up if you have many PC's in varuious locations in the house.