A agree with Stormknight. I am also a new developer and found it extremely useful to investigate other peoples code
for the most part devs seem to comment their code very well which makes it a lot easier to follow.
What I did was start from the beginning with trying to create and display text in a TopLevelControl with lua. This will help you figure out how frames work and how to manipulate them.
the wiki is the best guide in terms of understanding what something does if you can't figure it out
best of luck man!
If you're looking to change frames that already exist in game, check out zgoo it's a really handy addon for developers