You cannot import annotations into Kindle 4 PC, but anything you bought from Amazon should be synced with K4PC, including annotations. Not very helpful here, though.
You may want to take a look here:
http://www.clippingsconverter.com/
They can import a "My Clippings.txt" into a database and show it to you per-book, or export as Word, Excel, or PDF. It should help a lot with the readability vs. a
text file.