Problem about licence and copyright, worry me more than learning a new language

hi everyone,

I am a new firefox extension developer and just start build my first
firefox extension, I recently develop something that make firefox act
more like google browser.

So all my code done, but before I submit I decide to have a check on
copy right problem, that worry me.

My addon is actually base on two current work. First, I actually copy
and modified some XBL code from firefox tabbrowser.xml. Secondly, my
addon depends on another addon - ChrominFrame by Zero Fire (https://
addons.mozilla.org/en-US/firefox/addon/10091).

I go through the document, and find that firefox with tri-licence and
ChrominFrame is MPL.

I wonder what so I do explicitly in order to obey the licence (for
example, what comment should I include in my code), and since my work
do not include code frame ChrominFrame but instead change it by XBL,
should I also attach MPL header to my work, with original developer as
Zero Fire.

Sorry I am really new in Open Source Contribution, my English is
really bad and I get headache when facing legal problem. I mean no
offense to any rule, I just wanna to contribute to Firefox I love. So
could anyone give me some advice on it?

Thank you very much