how would i go about putting a pc hard drive in to ps3?
You need a laptop 2.5" drive. Any descent 5400rpm drive will work fine. There are tons of PS3 drive upgrade videos on youtube. It's very simple to do. Depending on how much disk space you currently have used on your PS3 will determine how long it will take to upgrade your drive.
This is the hard drive I upgraded my PS3 to. I upgraded over a year ago and have had no problems at all.
Edit: Make sure to sync your trophies before starting. Trophies do not get backed up. After you have the new drive in and the backup restored, sync your trophies to get them back.