1. i don't think it matters, in fact i don't know what gauge wire I'm using, i just use what ever i find in my class room
2. you can find LED calculators here:
Modding Basics3. hmm, i think the guys here on the board use
Mouser, once again i find mine at school
4. i also forget stuff, and then i try the search button, but it does not always help though, hope this helps