yes - you can reverse an RNY. However, they usually only do it for serious medical issues that can't be resolved any other way. I'm not sure why you'd want to go from RNY to sleeve, though, since RNY is a stronger surgery. Unless you don't really want to lose more weight (you said you've put on 60 lbs) and are more concerned about getting stomach acid back (not sure why you'd want this - plus GERD is a potential risk of sleeve).
I've heard of people having RNY revised to DS, when they reverse the RNY, create a sleeve, and then do the intestinal bypass part of the DS - but very few surgeons are qualified to do this. I would probably consider some of those surgeons, though, since they'd have the most experience (even if you just want the sleeve part).