Hello nobu,
I see you continue to work hard on the Event Guide module. Thank you for all your efforts!

I am still using the previous release and it is heavily modified. May I ask what actual files have changed so I may determine if I should upgrade? Or if I can simply copy over some of the files?

I would have to do much work if I upgrade but am happy to do so if it is necessary.

Thank you.
Hope

Upgrade doing just override, and do module update in module manager. At once after upgrade install, module proceed database update (when upgrade from 1.7 or before).

Of cause, you make backup files and database if you warry.

However, I don't know what modification in your module. In upgrade, module will be working, but modification function to be lost.

Thanks. Are there any security fixes/enhancements? If not, then I will not upgrade as I have changed php and template files. If the upgrade includes a security fix, please let me know.

Well, What version you seid about?
From 2.0beta there is no security fixes.
(but there is many bug fixes )

You can see detail of changes at language/english/changes.html in archive.