a name you want to have on network
SSID is the name of any WIFI distributer. SSID name of the Network
The SSID, in a nutshell, is your network name. So if your wifi network is called myWirelessNetwork then just put that in your ssid field. Your PS3 should be able to identify this automatically.
Your PS3 must have a wireless adapter installed if you want to connect to the internet wirelessly. Otherwise, if you don't you will have to use an Ethernet cable. If you have a wireless adapter installed on your PS3. You will need to connect it to your wireless router. Go to the wireless network menu on your PS3. Find the (SSID) network name of your network. Connect to it!
Nope, the PS3 Network is completely free.
After you PS3 has an internet connection you need to register and join the Playstation network
Yes, you cannot change your PlayStation Network ID. Maybe Sony will change this soon.