To answer your second question, you should check out this book:
Designing Audio Effect Plug-Ins in C++: With Digital Audio Signal Processing Theory by Will Pirkle.
The book goes through some basic DSP and walks you through how to make audio plugins. You'll code in C++ but it won't be hard because the book suggest you download a framework, RACKAFX, which handles all GUI events. All you'll have to do is focus on writing the formulas and storing the data in the right channels.
Good luck!