San Diego shift questions

Hi
I've got a couple questions that hopefully one of you can help me with. I'm a student and an EMT. I've got a part time job now that is fairly unreliable as far as hours goes. I'm thinking about looking for part-time or per diem work as an ER tech. One it'll help me get used to how things work on the "other side of the ER door." Additionally, from what I'm hearing it's fairly steady work. Maybe even too steady, but I'm ok with that. I want to work the ER when I graduate so I see this as a way of making sure that my preconceived notions of ER nursing are close to reality.
My questions are: what's the difference between part time and PT II? Also what is the real difference between part time and per diem work? With per diem work is there a minimum of shifts per week you need to work, and typically what is that number.
I'd really appreciate any insights you could give me on this stuff. Thanks in advance
aloha
Jim