[clo821]

No you dont have to call sprint to reactivate the phone.

Usually ppl hard reset their phones as a last resort when they have a problem with their phone (i.e. errors uninstalling programs, problems with GPS locks, etc.)

However, if I were in your shoes, I would hard reset to get a clean version of the phone. It would be like getting the phone out of the box (all the files your friend had in the phone would be deleted as well as programs that are not built into the rom for the phone)