The maximum capacity 2.5" hard drive you can buy that fits a 9.5mm form factor is by Western Digital and it's 750 GB. You can buy bigger capacities but they are 12.5mm thick and will not fit in the PS3's hard drive caddy.
After research I upgraded mine to a Samsung SpinPoint M7E HM641JI 640GB 2.5" Hard Drive SATA 5400rpm 8MB Cache. It's perfectly spec'd for the PS3 and does not cause any FMV judder, extra noise or overheating. Been using it for 4 months with no problem.
Then to backup, plug in a large capacity USB hard drive or pen drive and use the System menu on the PS3 to do a full backup. Then fit your new internal, allow it to format/setup then go to System again and do a restore. All my game data, settings, saves came across perfectly.