Diablo Game Questions Diablo Ps3 local coop questions

Good day all!

My girlfriend and I wanted to do play a local coop game and we've decided to play Diablo 3. Neither of us have played Diablo before and I hope someone would be able to answer our questions regarding local coop before we buy the game for our PS3.

  1. I've heard that it is quite a complicated process to play this co-op (need two separate user accounts on one PS3). So how do we do it exactly?

  2. How is progress saved? For example if I play using a character from User1 on PS3 and gf plays from a character from User2. There might be times where I'll play solo. Let's say we both played until Chapter 2 of the game. Then User1 progresses to Chapter 4 of the game while playing solo. (if the game has chapters, that is). Does User2 have to go over through Chapter 3 alone or User2 automatically joins User1 on Chapter 4?

  3. How about levels? If a character from User2 progresses to level 30 during our coop play, what level or what progress will she have if she decided to play solo from her own User?

  4. Seeing that this is not split-screen, how does the camera work? Will it be centered towards Player 1 and if we both go on opposite directions, will player 2 be out of the screen and must go blindly to where Player 1 is?

Thanks so much!