Is there a good source or book any one would recommend to get started?
There are a great many sources and books on this topic. It can also get quite in depth mathematically. I doesn't take long before the books and sources start getting into Ohm's Law and all of that. Fortunately your looking at reproducing something that has already been designed so all of that isn't really needed. So just Google the parts to get a better understanding of the,.. Wikipedia should be a decent source to learn about them.
I use to take electronic classes back in high school. But have forgotten most of what little i learned over the past 12 years. So as a refresher before buying the arduino i picked up a helpful little kit. Comes with a project book, some components and a breadboard. The project book was good about teaching some of the basics without diving into all too much of the math behind it all.
Part of the wide variety of parts is different manufactures but most of the verity is in there specs. You need to have a pretty good understanding of you circuit and the power needs across it. But the project your working on tells you all the specifics you need. So enter there full descriptions into the catalog search and see what comes up. Then choose the cheapest one that's inside the parameters you need.