> I'd like to gain an understanding of the technical aspect of things to the point where I can at least understand how much work a feature request translates to.

First, you should read "The Mythical Man Month" and then start learning about the specifics of coding. Doing it in the reverse order is the path of painful and expensive mistakes.

EDIT: I would suggest the expanded anniversary edition, rather than the original edition of the book. Also, having a minimal understanding of ancient systems (pre hard drive main frames) is helpful but not required. You can always ask here on HN about the difficult, odd and adventuresome aspects of old hardware.