First, read all what you want to know on http://linuxcnc.org/ There are many people, they can help you, the owner of Mesa as well as some ingenieurs who use this parts in their application.
You need a PC with Intel or AMD core not really big performance, but depends from the motion card, it should have a latency, that you can test with a SW that is part of the program.
While the test is running, you should use some processer relative tasks, view some movies, run 3D-Cad or similiar programs, copy bigfiles.
Than you can see, if your PC is good enough for LCNC.