In this blog post I walk through the process of how I go about extending emacs (specifically a 3rd party plugin) and tailoring it to my specific problems.
I'm definitely not an emacs pro, but I've written a few packages in emacs and have a cursory idea of it's vast powers! Happy to answer any question.
For anyone interested, my emacs config is at: https://github.com/oxalorg/.emacs.d