These are good questions, not noob ones!
1) Look in your owners manual for the QVL. Buy make and model that it says will work.
2) I like 8Gb as a minimum of Kingston 1333 or 1600MHZ. Also like G.Skill, Corsair, Patriot, etc. Buy the cheapest that fills the need.
3) An SSD is the biggest performance boost you can give a computer. An HHD is always the biggest bottleneck in a build. So yes, if you can afford the luxury, buy one!
Sorry, I can't help with store links....I live in CANADA (and glad I do). It is one of the few places in the world that people are not "afraid" all the time.