You are getting good advice but I am curious about the reasoning behind all this. If you don't know/understand how these systems work, how do you know you need to change them? Are you doing this because someone told you that it should be done? Did a shop sell the thought of these modifications?
Maybe the whole thing would have worked fine just the way it was. I always suggest that people first use what they have and then take baby steps into upgrading. It is easy to waste money on upgrades that someone else recommends that in practice are worthless to you.
