I am a blogger and just curious about how Google indexes blogs in case they are modified. When an already published blog post content gets edited or modified, does Google re-index it?
The simple answer is "Yes".
Google will have a reindexing schedule based on how "important" it regards the content. For example Stack Exchange sites get reindexed very quickly as a search based on your title for this question will return this question already (hopefully).
So, at some point your blog will get reindexed.
Agree with "Yes, eventually".
Provided your blog is set to be visible to search engines (under Settings > Basic > Privacy ), at the time when Google's search engine bot visits your blog. Which may be anything between seconds and days after you edit your post.
One method that seems to speed up the process is Sharing the post on Google +.