CvReligionScreen.py is what I meant. It is the Religion Advisor screen.
CvRandomEventInterface.py is included in the "event-related files" I mentioned. This one is from the UP. You may want to compare it to yours to see if it has anything you do not. Same for CIV4EventInfos.xml. Did you add your own events? Are you using the UP?
Yes, CvMainInterface.py is a huge part of BUG. If you have your own changes to it, you should merge them in. If not, take BUG's. This applies to every file, really. Do a diff using WinMerge to see what's different.
CvScreensInterface.py is also mandatory, but Next War adds some stuff to it that must be included. This file you definitely have to merge.
Ouch, you could have downloaded all of the BUG files with a couple clicks.

Google TortoiseSVN to get the Windows program and read our
docs on accessing the SVN. Follow the instructions for the Mod install.
My time is also limited. All the time I devote to helping modders takes away time from BUG. I'm happy to help you learn, but I just can't be in the "let me do it for you" business anymore. I suggest posting some more general merging questions to the SDK/Python forum. To learn some Python read
How to Think Like a Computer Scientist. This is a great free online book on computer programming using Python.