I actually just came in from the garage from spraying a final layer of clear on my latest custom case (#4 for me). Personally I don't use the 120mm fans in my custom cases. I always use 80mm" becuase it means I can just use a 3" inch hole saw, which is relatively common, larger sizes get pricey quick. As for how many that just depends.
Something to think about too, I never have understood why they put the two hottest things next to each other inside computer cases (PSU and CPU). In the cases I make, I always put the PSU unit down in the lower front section, and relocate the power plug to the back of the case again, using some 14 guage wire. If you don't want to void the warranty on your PSU, you can also use the female spade terminals connectors (to plug into your current PSU), and then use a plug from a junk power supply to add to the back of the case.
Obvisuly one fan in the front and rear, maybe one down near the video card, to help get fresh air into it. Don't go to nuts on the fans as its not really necessary, and your case will get rather loud, very quickly.
i was told that you want more fans blowing in than out or u will create a negative air pressure and draw dust in
Actually, in theory, you want the same amount of air coming in as going out. No matter what you do you will get dust in, so I wouldn't make keeping dust out a primary concern. Also normally you aren't really going to create enough negative or positive pressure to care, computer cases just aren't sealed up tight enough for this to really affect you.
As for paint, always keep in mind that paint doesn't stick that well to powder coat and no matter what you will want to sand the surfaces first. You can sand off all the powdercoat if you wish, or you can use some sort of adhesion promoter, which is available at almost any auto parts store (Used to make paint stick to different types of metals and plastics). Always thin, light coats at first, if you don't the paint won't stick well. Once you get the primer/ adhesion promoter on the case then you can go back to a regular coat of paint for each layer. Oh and after you get down sanding the case, and wipeing the dust off, use a clean rag and wipe it off with rubbing acohol to get any oils and such off it. Also paint just one piece at a time, if you try and paint the whole case at once, you won't be able to get the paint wet all at once, meaning the paint won't be shiney in certain places. (Oh and as for sandblasting to get the powder coat off, be careful some sandblasting systems can be a little strong, and warp certain peices, and damaging others, I had to start my latest project over after trying to sandblast off the paint, after a painting mishap)
Once you are happy with the finish, go back over with a layer of clear coat, make sure you get an automotive grade clear, and give your case pieces (idvidually) a couple of layers of clear, this will help prevent scratching, and will make the case shiney, and cover up some minor blemishes in the paint.
As for a window you can get a window kit from where ever, as it will be just a square piece of plastic. On my latest case, I used just a piece of plexi glass from the local hardware store, they sold a little piece to me for a couple of dollars, then just cut it to the size I needed, and drilled the bolt holes.
If you are going to paint the chassis (The inner frame of the case), paint what won't show first, that way any overspray into areas that will be seen, will be covered up by the last coat of paint. Try and break the pieces you paint down into the smallest pieces you can, the smaller they are the easier it is to get a good finish on them.
As for the cuts, I've always used an angle grinder with a cut wheel, and have found the smaller cut wheels for the air rotary tools work best, and allow the most precise cuts, as I don't have the patience or a saw good enough to cut through the metal. You shop teacher should be able to recommend what would be best for making these cuts.
For the front make sure you use an adhesion promoter on this, as it is plastic, and most paints won't stick to well to it. Some front panels I mark off and drill extra holes, to make a "grille", and to allow more air to flow through. You could always incorporate some sort of design into these holes.
You could always make a new front out of a mold, using fiberglass (or even carbon fiber, but it may be a little hard to find locally). This may be a little more complicated than what you were thinking of, but just another ideal.
My Desktop: <A HREF="http://Mr5oh.tripod.com/pc.html" target="_new">http://Mr5oh.tripod.com/pc.html</A>
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