just the three black bolts on the top. When you put it back on make sure you don't over tighten them because they will just snap. The hole they go into is only as deep as it needs to be so it goes in so far and then basically locks up, once you feel that don't try tightening it any more.
Clean it with whatever you have to hand, I quite like using carb cleaner for stuff like that. Then some metal polish such as peek or autosol.
a parts washer is just a bath of nasty chemicals you put car parts in to clean them.
Get the paint from anywhere really, no need to buy it from VW. You want to use a high-temp paint really.