Your Model PS3 Can Sometimes Be Modded and Sometimes It Cannot.
Your model is the model that Sony started blocking downgrades so custom firmware could not be installed.
Min Ver checker can be ran on your PS3 to see what is the minimum version firmware that can be installed on it.
We can do this for you free of charge or you can do it yourself by downloading MinVerChk and running it on your PS3.
MinVerChk can be downloaded from here.
The PS3UPDAT.PUP file needs to be place on a USB drive with the following file structure x:/PS3/UPDATE/PS3UPDAT.PUP (where x: is your USB drive letter. The folders PS3 and UPDATE need to be in capitals) Then run System Update from the Settings menu.
If firmware version 3.56 can be installed on your console we can downgrade and install custom firmware on your PS3.
If your PS3 can only be downgraded to version 3.60 your PS3 can unfortunately not be downgraded and have custom firmware installed :-( But you can install PS3 Homebrew Enabler (PS3 HEN) check out www.psx-place.com for more information about HEN