After successful treatment for hep-c, what are the chances of the hep-c virus returning?

<1% if SVR. If you have successfully been treated for hepatitis c and your virus is negative 6 months after your last dose of hepatitis c treatment. You have achieved svr ( sustained virologic response). These individuals have <1% of recurrence.
Depends. On the genotype of hep c and your viral load. For the most aggressive type, 1a, about 60-70%.