OK lets see...
Im not sure about the game pad and joytick but about the monitor, I think it would be useless to take it out of the case, theres really no point at all, just looks messier with wires if you ask me, and about painting it, you wouldnt even have to, just set it in your cabinet and make some sort of a monitor bezel, and then cover that with a sheet of plexi glass in front of your monitor, for a bezel an easy thing to do would be mask out the areas of the screen on your plexi glass then spray paint the outter edges black, do you get what im talking about, if not just post it and ill try to explain it better.
Its going to be hard not spending any money, your going to need to buy wood, ( a cheap wood is particle board), your arcade controls, paint, lighting, t molding, and various other things, if you want prices just post and me or someone else could help you out, dont be afraid to keep asking questions, cuz im building my first cabinet too and im only 15, i didnt know anything at all, so i asked alot of questions other people might have laughed at, hope i could help.