Check out these three links:
The Allstar folks are the ones who offer the ACID Linux distribution which has all the software you need to run a node. Much of it is preconfigured. It's essentially CentOS 5.11.
So, buy the URI and the right cable for your radio. Download ACID Linux and install it on an old PC. And hook up the radio. Then configure and adjust the audio tuning in the software.
Most all the configuration can be handled via the Allstar portal. You set the configuration there and and it actually pushes it onto your computer. You do need to setup port forwarding on your router for this to work.
If you wish to enable Echolink, you need to forward those ports as well. This software will do Echolink with very little extra effort. But you will want to change your callsign to have the -L suffix and switch it over to "sysop" mode.