The fewer changed files in your template, the more likely it is that you won't actually have to compare and merge them.
You need to compare the changelogs against the files in all of your custom template folders; only files that appear in both places need to be merged.

Also, a few of the changed files are mostly housekeeping or code optimization, and will still work with the old version. I wouldn't rely on this, though, unless you know exactly what you are doing.