You can't put a hard drive in the slim PS2. On the fat on a panel comes off and there's a bay and a network connector. You slide the HD in the bay with it's connectors facing out. The Network Adapter replaced the bay cover. It plugs into the network connector and the Hard Drive.

I don't know about the rest. I've been running the orginal HDLoader off the DVD. Supposedly there's a way to install in on a memory card, but I don't know how to do it.