I know for a fact that you can not swap out a 360 hard drive with a ps3 hard drive even if you take them apart.
You have two options:
1.You can buy a new SATA 2.5inch hard drive and swap out the old..
Video:
YouTube - PlayStation 3 Hard Drive Upgrade (HOWTO)
2.You can buy a huge 3.5inch 400 gig SATA harddrive and use it as an external...
Video:
YouTube - Replace the HDD of PS3 60GB(2.5inch) to 400GB(3.5inch)
Note: Make sure they' re SATA 3.0...