"Cuerpo" is simply the "body", in this case he definitely is referring to one of the two main barrels that form the focusing helicoid.
If the focusing ring is stiff due to the lens being dropped then one of those two barrels (most likely the outer barrel) has deformed and this is preventing the focus to work smoothly.
"Barrita" is just "little bar", you will have to let you take a pic to see which bar he's referring to. On the other hand, most (all?) focus helicoids need one or two "little bars", usually brass, that are the ones that prevent the helicoid from turning and thus let the lens slide back and forth. So one of the helicoids are kept from rotating by the "little bar" and slides against the "little bar". Perhaps we can call it "guide pin" or "guide slide"
Google for pics of any lens being dissasembled and you'll find said bar.