Yes, you can copy/transfer your saved games into your USB drive.
I myself has upgraded my PS3 console from a 80GB HDD to a 500GB HDD.
In order to back up your file go to System settings>Back up Utility> then select Back UP. Once thats over just remove your memory stick and viola!!
Oh if your ps3 is broken, upgraded your ps3's hdd or you bought a new ps3 and you stll want to use your original PS3 ID then select the Playstation Network icon on your PS3 and select the one saying that you can make your own PS3 online ID.
Press that and now when the blue screen appears, select the bottom button, it says something like this: use my original PSN ID.
p.s make a duplicate copy of your game saves and put them into your computer, if anything goes wrong with your ps3.
Hope this solves your problem 
- gtone339
