Welcome to the forums and congrats on rescuing your first piggy! (If you fall in love they are irrisistable so you will be sure to have more!)
About the squeaking, I definitely agree about the fruits and veggies. Parsly is one of many pigs' favorites, and you give about 10sprigs a day(on the days that you chose to feed them parsely.) Also, my piggies enjoy apples alot, but I only give them apples once a week because too much can lead to watery stool and mouth sores.

My piggies enjoy some baby carrots once in awhile. I find that they like baby carrots alot more than large carrots because the baby carrots are so nice and juicy - where as the larger ones are drier. Also, most piggies also like celery! You can feed them bananas(with the peel) or even oranges. Just be sure to check out the shopping list in the food section of the forums!
Are you adding Vitamin C supplements to his water? Guinea's don't naturally make Vitamin C in their bodies, so you have to add it to their water and also give it to them in good pellets and fruits and veggies. If he doesn't get enough, he might develope scurvy. Also, when you add it to his water make sure that you are refreshing his water daily because the vitamins tend to deteriate after only a short amount of time. (oh and you can buy the vitamins at any pet stores and stocks up with small animal supplies - just make sure it's for guinea pigs and not rabbits.)
THe vibrating is normal. Sometimes when my piggies are talking to each other they vibrate with excitement, and sometimes when I take them to the vets they vibrate because they are scared. just look at the situation - Is something stressing him? or does he seem relaxed and not stiff and alert?
They are very social animals. He probably will need a friend unless you are paying attention to him every waking hour. (which is impossible.) But be very careful. There is lots of "piggy porn" on the internet that will help you check his sex for sure. This is important because you give a unneutered boar a sow, she will most likely get pregnant - and piggy pregnancies can have so many complications and are sometimes fatal! So make sure you know for sure, and aren't just going off of what you were told. Then, if he really is a male, then you need to think about a very young boar (not yet "teenage") so that you can introduce them and hope for a successful bonding. (Doesn't always work, they sometimes fight.)
There are many many breeds of guinea pigs - and it's almost impossible to find a pure bred of any sort. Because you can never tell their ancestory or family history, basically you go by the descriptions of each breed.
Heres a list that's easily accessable (looked it up on google)Breeds
American - short, smooth hair
White Crested - short, smooth hair with a white rosette on top of the head
Self Crested - same as White Crested, but all one color
Abyssinian - Short, cow-licked hair (body covered with rosettes)
Peruvian - Long hair (floor length) that covers the face, making the piggie look like a mop
Silkie (Sheltie) - Long hair (floor length) that goes back towards the body rather than falling in the piggie's face (also known as a Sheltie in the UK)
Teddy - Short, kinky hair with a course texture
Texel - A Silkie with a curly coat that falls in ringlets
Coronet - A Silkie with a rosette on its head
Merino - A curly-coated Coronet
Alpaca - A curly-coated Peruvian
Skinny Pig - A piggie with no hair anywhere on its body (rather rat-like)
Satin variety - An extra sheen to the coat that makes it look satiny (pearlescent)
American Satin
American Crested Satin
Abyssinian Satin
Peruvian Satin
Teddy Satin
Coronet Satin
Rosette:
A section of hair that looks like a whorl that radiates from a center point. A starburst of hair.
Hope all is well and good luck! Let us know how it goes!
Best of luck and thinking of you,
Kay ^-^