Chocolate Sweetening in Ganache
Honestly, I wouldn't worry about it. It depends a little bit on the ratio of cream to chocolate you're using, but your ganache will turn out fine without adding sugar. If you're only using, say, 2 Oz of chocolate for your whole batch then it's worth adding some sugar to compensate. But if you're making enough to fill or cover something, the reduction in sugar would be hard to notice. You can (and in my opinion should) add a pinch of salt as well, which will help balance the flavors a little bit. 

If the ganache does split or curdle, there are ways to fix it as well, usually by adding a little more hot cream at a time and whisking.