It's all dependent on your firmware version. The highest "hackable" official firmware (abbreviated OFW) is version 3.55. You need to be on this version in order to install custom firmware (abbreviated CFW)
You will see people with their post signatures that say "PS3 4.46 CFW" etc. etc. This is due to the LV0 encryption keys being leaked last year. This is good and all but you still need to be on 3.55 in order to install the higher CFW's, since it contains the exploit used to install hacked firmwares.
According to this wiki
http://www.psdevwiki.com/ps3/SKU_Models you have a PS3 model that can be lowered to 3.55. To do this you need a hardware flasher, like mentioned in the post before.
Do you research, you might find an individual or business in your locality that does PS3 repairs. They will most probably do flashing as an extra service, if you don't want to attempt it yourself.
Good luck.