Instructions
Decide which PS3 version you want. You could get another 40-gigabyte PS3, or you could get one that has a larger hard drive, up to 320 gigabytes. The 40-gigabyte PS3 is no longer in production, but you can often find from retailers. Sony also has the PlayStation 3 Slim, which has almost exactly the same features but is smaller.
Purchase a new or used PS3 from a reputable seller. See resources for Sony's "Where To Buy" page.
Back up your games, if you prefer. If you do not back up your games, you will lose all of your progress and saves. You can back up your data by plugging in a USB flash drive and navigating to "Settings," then "System Settings," then "Backup Utility" in the XMB Menu. You cannot back up your trophies.
Turn off and disconnect your original PS3. You can actually leave all of the cables in place for the new PS3; that is simpler than pulling all the cords out and then putting in new ones. You will need to unplug the PS3's video and audio cables, its power cord and any other cords you have connected, such as an Ethernet cable or PlayStation Eye. Note that if you use an HDMI cable to connect the PS3 to your TV, you will not have separate cables for audio and video since HDMI handles both.
Plug in the cables to your new PS3. Anything that you unplugged from your old PS3 should be plugged back in to your new PS3. You will need to plug in at least the power cord, the video cable and the audio cable(s).
Turn on your new PS3 and follow the on-screen step-by-step setup process.
Plug the backup peripheral from step 3 into your new PS3.
Restore your data from your old PS3 system. The restore feature is under "Settings," then "System Settings," then "Restore" in the XMB menu.