Not quite so frustrated..
My previous post was about frustrations related to Extension development. I poked around the MozillaZine forums to try and see if I was a complete moron or if in fact some other people are having the same kinds of problems.
I was really happy when I encountered this thread which I think has a few good points. 1) It shouldn't be this difficult to create an extension for both FF and TB (I guess that's short for Thunderbird) 2) There is always some smart guy out there who actually knows how easy it is.
In the thread the Extension Wizard is mentioned. I wish I'd known about that one when I started out. Basically it does all the boring and unnecessary complicated stuff for you. It creates an extension with the preferences you want.
So for anyone starting out with extension development I think this would be a huge help for both getting started and to get a sense of how one should design code for an extension.