Again, upgrade times for the twin will vary depending on where you're based. If you're willing to be out-based (that is, not RDU), upgrade is immediate since all but one out-based run is a twin. If you stay in RDU, it can take several months. It's always hard to say now that the regionals are hiring again. Unless something changes in the next week, plan on being RDU-based.
Upgrade training is a combination of several hours of ground school on systems plus several training flights followed by a check ride.