Spartan-720, it just depends on how much you want to do to your suit. If you just want a cardboard or paper suit that you can paint and carefully wear, you can probably do that in a month or less (even if your taking your time). But if you want to fiberglass it and everything, my guess is that it will take more time than that.
Spartan-183, the virus warning is just something windows warns you about whenever you download an executable (*.exe) file from an "untrusted" site. Any executable file could potentially contain a virus, or itself be a virus. Windows is only warning you of that fact. But Pepakura straight from their site contains no virus or spyware.
I haven't used the screensaver, but I didn't think I needed it either. Just fold the peaks and valleys like you are supposed to and then tape or glue it by the numbers and it should be pretty easy.