im letting my brother keep my old PS3 and im buying another one tomorrow....how do i keep my same PSN and everything....i know i lose the stuff i saved but im not worried about that, im new to this so someone help me.

you might be able to copy some, probably not all, gamesaves onto a USB drive. As far as demos, downloaded PSN games, and add-ons, you just need to sign up for the PSN on the new console and choose sign in with an existing account when prompted. From there you can go into the PS store and select the "view downloads" option in the upper right hand side and re-download everything associated with your old ID.

you can also try to back up your system right now using the back up utility. You will need a pretty large external storage media, like a USB external hard drive. Then, on your new system, you can try a restore operation. Not everything will transfer, but it may save you some time.

I think the only thing that won't transfer is PSN purchased videos. Even the non-copy-able game saves get backed up.

If you have space, it may be worthwhile to do 2 backups as they often don't restore correctly. I would also copy the save games that allow it to a USB stick just to be safe.

FYI, you missed out as Amazon had the silver PS3 with MGS4 for $399. They're gone now. I got one before to replace a PS3 and they are gorgeous.