Il Mio Problema
Had a bad hard drive. My son pulled his PS4 onto the floor while playing a game with his controller charging.
La Mia Riparazione
Easy. Just download OS, swap the drives, boot up PS4 and select the last option on screen and we were up and running in 30 min.
Il Mio Consiglio
Just read the instructions on Sony website and you will have no problems.