I think the real take away is that this same experience can be applied to any large open source project that seems daunting to new comers, not just for Mozilla.

I had a similar experience with emscripten (yeah I know, Mozilla too) initially. So I start working on a project with the following steps:

- Download code - Setup environment - Run test suite (if exists) - Play with simple bits of code by hard coding changes and building it to see it's effect. - ... sleep? - Attempt baby bug first