To do the hacks you are talking about you would need a jailbroken ps3. To do this your ps3 must be on firmware version 3.55 , however if you updated to latest firmware update then , jailbreaking is no longer possible. However there is a piece of hardware called an "e3 flasher" which basically will downgrade your new firmware to a previous firmware.
If you do jailbreak it means your system is now open , this means more files are available for you to view(such as the mw2 patch , which is a file which contains rules about the game).
To get access to these files you need to install a package file to your ps3 called "FTP Server".
You then install a program to work with FTP Server on your computer such as Filezilla.
This now means your ps3 and pc can communicate , from here you can find and open the mw2 patch , and edit it to your liking.
if you don't or can't jailbreak there are always usb hacks which don't require a jailbreak(although these are usually not as good) hacks include ,, modded clantag , modded classes names , sensitivity hack , no recoil hack and tenth prestige hack(probably more hacks).
hope this helped