You should definitely retake. You haven't elaborated on the preparatory materials you used before taking the GMAT. Based on various debriefs from 700+ scorers alone, I can tell you to get the MGMAT SC
Guide, and the Powerscore CR
book and work heavily through them and master all the concepts. Because, sentence correction can be mastered. It's like math in a lot of ways - there are simple rules and lots of them, but once you get the grasp of the spectrum of rules and see how it is applied on paper (computer :D) you get the hang of it slowly. But this happens only with practice. So, do that (with the CR as well) and then when you feel you are completely comfortable with that move on to the OG 12
and OG Verbal
Review. Beyond that, take a few practice tests and see where you score.
As for RC, I think there are various threads detailing how to improve your RC score. Just do a search for them on here, and check out the open source GMAT Club Grammar Book
too. They have some pretty succinct explanations going on there.
But before all this, breathe! A 610 is by no means "shameful" but if you're aiming top 20, yeah, you'll need to cut it better. Take a week off. Don't touch the GMAT books (No, sneak peeks are not allowed either. And strictly no cursing at whim). Relax, clear your mind and start afresh.
Hope this helps