|"Does it matter which slots the faster RAM is installed into, and if so which sticks should go where."|
Yes it matters only if u plan on running dual channel ram which is faster.
to run dual channel ram one must have the same ram speed, size,timings.doesnt matter where he puts them in wut channel all that matters is that they are the same specs thats why u see sometimes ram companies like OCZ sell dual ram boxes:http://www.slcentral.com/ddr-ram-comparision-corsair-ddr400-transcend-ddr500/Corsair%20Box.JPG
just one question why would someone need 12GB DDR3 ram?
computers are a second home