Hi there Walter, I take it you have got a plasma to start with.. For the height control you can do it manually or just get one of these units to put on to your plasma..
Proffessional Compact CNC Plasma THC Controller ( Torch Height Control ) | eBay

They are very good and save a lot of headaches if you choose to cut thinner metal it can warp and cause you problems.. this unit takes away all the pain.. there are some pictures and instructions of the setup at the bottom of the page, ive fitted a couple of these and was very impressed..

I am building a plasma/router myself at the moment. I will keep an eye on your thread and if i can help in any way let me know, ive been using the plasma at least once a month lately as im building an american hotrod (40/32 ford with hemi motor) as a side project, so you can see my need for a cnc as well for fabrication

Rick