How can you tell if your guinea pig is
There are a few ways of telling, especially from the sounds they make, If you hear it making a sound sort of like purring this means it is enjoying itself maybe because you are petting it or while grooming itslef. If it whistles this can also mean it is excited. Wikipedia has sampled the sounds the guinea pigs made and has the meaning of each one, here is a link:
If it purrs or lowers its head it means it is having a good time and its happy!
Welcome mate hope it helped!
Other people asked questions on various topics, and are still waiting for answer. Would be great if you can take a sec and answer them