To downgard in general yes need a Hardware flasher, and a dongle. You have a NAND PS3 so, you must dump both NAND chips. It can easily lead to a bricked PS3 if you don't know what you do and if your soldering skills are not that good.
Save yourself the headache of a bricked PS3. And don't waste your money on buying a flasher. Just find someone who can do it for you like racer0018. Check this --> PS3 Unbricking and Downgrading Service