Good sources for learning basics/My basic Questions

[coolhotdogguy]

So I saw a YouTube video and decided I wanna try this metal working stuff out a bit. I have a bunch of questions and was wondering what are some good sources to check out to make sure I do this right and safe?
Guess I'll also ask my questions here!

1. I'm thinking of casting aluminum and I would like to use old soda cans. Will this ruin a clay graphite crucibal?
   
   
2. Any ideas where to find excess aluminum for melting?
   
   
3. Can I temper my crucible in a propane forge like in the video?
   
   
4. How important is borax in getting my clay graphite crucible ready?
   
   
5. I have a clay graphite crucible and a silicon carbide graphite one. What temperatures can they handle? What is the difference?
   
   
6. Are sand molds a good place for a beginner to start? Any tips?
   
   
7. What are good ways to finish an aluminum mold? Polish? Sandpaper?