New to SoundFonts-Any Good Beginner's Guide?

Hello. I've been growing dissatisfied with some of the vanilla instrument sounds in MuseScore (goddamned C-clef strings), and so I've been looking into some installing some soundfonts. However, I'm more than a bit lost. Can I use multiple soundfonts in one score? Can I add effects (I.e static noise) with them? I've heard they can be edited. What program (preferably free) do I need to do this? How much can I edit it exactly?

Are there any good beginners tutorials to answer these questions?