Yes.
Click on the related links section indicated below for the instructions on how to sex your guinea pig.
This is easy to do. Like most male mammals, the male will have a penis and the female will not. You may have to move some fur to see it.
No
search on google - 'guineapigcages.com' they have a lot of helpful info and even a whole page on sexing guinea pigs. remember - boys have an i... girls have a Y :)