Can I buy all the parts?
Almost. The only thing you cannot order (yet) is a rack or holder for the plasma tube. You will need something to hold the tube for you. It has high voltage electrodes and you should not touch the electrodes or the tube while the tube is running. I bought a reasonably cheap IKEA shelf and cut two holes in it for the tube, it does the trick. A little imagination will get you a long way.
Also, there is no off-the shelf enclosure yet with holes for buttons, sockets, displays and switches. You’ll have to drill those holes yourself.