To go from analog to digital (or the other way 'round) you have to go through an A/D converter. This process is lossy. Really good A/D converters (like the ones in the H8000 and the ones in your FireFace) minimize this loss, but the conversion is still imperfect. I prefer to get my signal from the (analog) instrument into the digital domain as directly as possible. Once the signal is in the digital domain, I keep it there until I'm ready to hear it. The cool thing about digital is that you can move it around and manipulate it in many different ways without introducing noise or degrading it.
Sorry, I don't know one website that teaches you everything you might want to know. There are how-to book and magazines devoted to many different aspects of electronic music production that are worth reading.
