Help needed please to copy game saves data, my ps3 is being replaced!!!!!! :(

Hi, 2 days ago whilst playing call of duty 4 online my sound started to cut out, then the game froze, i restarted it and it did the same thing.

Then i got the dreaded - error 80010514, which (according to the someone at sony) means your ps3 is screwed and needs to be replaced.

Ok, i thought, at least they know what it is and the replacement is going to be quick (monday)

But, how do i copy, back-up my game saves data for my games?

Especially for call of duty 4 (im on prestige level 5 (10 days worth of gameplay!)) ??

Please help, i have a 40gb model, so no memory card slots, so i assume i can use a usb flash device?

If so, what size? and can it be any make?

Thanks in advance for any help, i need to save my call of duty 4 data, i'll kill myself if i have to start all over again!!