1) Look at the AMCAS instruction manual for information on how it converts your grading scale into a standard one. In short, it'll take the grades as reported on your transcript and convert them to a 4.0 scale.
2) No one will care about a few Bs and Cs on your transcript, provided your overall GPA is a solid A and you generally get As in your prerequisite classes (Bio, Chem, O Chem, etc).
3) Talk to your science professors. Tell them you're interested in getting involved in some kind of research and ask if there are any projects you can help with.