Well if you want to go all the way happs sells a golden tee fore control panel, assembled with decals, trackball, and all buttons. It's the newer CP design, not the older one with grass and stuff.
CP is 180 bucks. To break down the cost of building your own, figure the trackball is 90 new, although it's on sale right now, buttons will be about 9 bucks, printout of the art will cost you some money and not be as good, and you don't have to spend time building it if you just buy it outright. Also you don't have to worry about it being poorly built or making mistakes on it if you are not good at that sort of thing. It's also going to be friggin sturdy because it's designed to be thrown in an arcade with a bunch of drunks beating on it.
So I guess if you want to take the plunge and this is strictly a golden tee CP I'd say just buy the happs one and save yourself the headaches. It's the most authentic and probably highest quality that you are going to get unless you are good with tools.