First film camera? I need help? (NIKON F55 FILM CAMERA)?

I know more about digital SLR cameras than film cameras. In fact, I'm sort of clueless about film cameras. My friend bought me a second hand Nikon F55 but it looks untouched and still usable, with a 28-80 lens and a roll of film already in it. Because I know nothing about it, I have some questions: 1) I... show more I know more about digital SLR cameras than film cameras. In fact, I'm sort of clueless about film cameras. My friend bought me a second hand Nikon F55 but it looks untouched and still usable, with a 28-80 lens and a roll of film already in it.
Because I know nothing about it, I have some questions:
1) I opened the film compartment bit and exposed the film to light. I didn't know this would affect the film until my mum told me. The roll of film was just all black, I don't know if it's been used or not. What will happen to it? Is it ruined? The brand of it is Fujifilm and how much would another roll cost?

2) I need a battery for it, as it didn't come with a battery. It needs two CR2 batteries. Will any CR2 battery work? Is it rechargeable? Can I just buy them off ebay or something?

3)Any other tips/pointers?

I'd really, really appreciate it if you answered. I want to learn more about film cameras and hopefully start taking my own pictures on it :) I know I sound like an idiot but I've never handled a film camera before.
3 answers 3