Hi,
no worries, the first line is so big because of a stray "=" on the next line, underlining the first to be interpreted as a heading.
I'll move this thread to the General Programming & Plugin Discussions category, because in the end C4D does not provide any means to provoke UAC, nor do we deem it necessary inside our API as it is a pretty system specific thing. Yet, the discussion might lead back to C4D related questions, and then I'll either happily move it back or we'll have a new thread in the Cinema 4D Development category.
In general I think, it would probably be better to convince your users to install the plugin into either the plugins folder in the "user folder" or even (assuming R20+) a completely separate directory added to the users prefs.
Another thought, while definitely possible with Python, I'd say an update mechanism should change/replace files while the main application is running. After all you can not be completely sure, which files the application decides to lock at certain points off time, in which case your updater would probably run into issues. My recommendation is to rather update by restarting the main app (for C++ it's inevitable anyway).
Cheers,
Andreas