What kind of paint is best for a plastic case?
You can use various paint types. There are paints made specifically for plastics, such as Krylon Fusion and DupliColor vinyl and fabric dye. You can also use acrylic lacquers and oil enamels, either with an appropriate primer for plastics underneath or some already come formulated to stick to plastic, such as Rust-Oleum Painter's Touch.
Is the paint surface noticeably different from the stock surface in terms of touch?
Yes, QFR comes with a very thin layer of rubberized coating that gives it color and texture. The gunmetal color is a fine rubbery layer over black plastic. The new texture/feel of your painted case will be of whatever paint you choose for it. It won't be rubbery though. And you'll want to sand off a fair amount of the rubber coating prior to painting.
How easy/hard is it to disassemble a QFTK?
Remove one screw from the back, use an old credit card sliding it in under the top cover along the back and front to pop open plastic tabs. There are probably videos of this.
I heard that its a relatively simple mod, but I have no previous modding experience. Are there any good modding guide/resources for beginners like me?
Thanks!
Yeah I think it's not that bad, especially for simple white. I helped someone paint their Ducky white with oil enamel, so if that's what you want, send me a PM for tips. In any case, google computer case painting as well as specific questions and do some reading. Then practice on random plastic or scrap metal. Only use very fine layers of paint. Multiple fine layers > thick wet layers, if you wish to achieve a neat uniform look that will cure well.