I'm new to the enchanting thing. So far I've destroyed an enchanted bow and created an enchanted bow that deals more damage. Before I go ahead and try, I want to know if I destroy a Saarthal amulet with spells cost 3% less to cast, can I use the enchantment to enchant scaled horn armor?

Save your game, do it, see what happens. Armor is funny sometimes - enchants you think should work aren't available. If what you want doesn't work, you have a save game prior....

Yes. Certain enchantments can only be used on certain pieces ie. chest, legs, ring. Spell% less to cast can be enchanted on chest armour


Edit.
Your better off saving before you do it, then load latest if your not sure on enchantments

i don't think you can disenchant the saarthal amulet, but as far as enchanting, i use it, my enchanting skill is about 80 and i take all 5 perks at the bottom the enchanting skill tree, but thats it, no other perks from that tree, to raise the skill just get a lot of small soul gems and enchant daggers or anything else, and that will raise your enchanting skill, i enchant all my gear and all my followers gear.