|Almost any router designed for a home network will do, it is just a matter of deciding on price. Don't get one with a built in modem as you already have one. |
As for setting it up, that depends on what you buy. They are all different but they do come with comprehensive instructions but it is not difficult.
Something like this will do. It does say cable router but it will work ADSL.
Just plug the modem into the WAN port of the router and each computer into one of the LAN sockets and run the configuration. It will probably work out of the box with the default configuration.