Hiya! Welcome to the forum!
I can't help with the rescues part of your questions, but I'll do my best with the rest!
It would be an idea for you to get two, rather than a single piggy. You really don't get the best out of piggies unless you can watch a pair of them doing what piggies do!
How to prepare:
There's not much for you to do other than find a suitable cage (4ft wide and 2ft deep is reccommended and required by most rescues!). Outdoor hutch you need to make sure they're 2 feet deep as many commercially available ones aren't that deep! Indoor cage, you should look at something like the Ferplast 120 or bigger if you can afford to go bigger.
You should also look into finding a piggy savy vet too, just in case of emergencies. Guinea pigs on the whole are surprisingly hardy little critters, but things do happen from time to time and it's always advised to register with a suitable vet just in case!
Obviously apart from that you just have to buy the accessories (bowl, bottle, food, chew toys, treat sticks etc) that you want to get. You'll get changeover food from a rescue if you've chosen a different food, or you can wait till you get your pigs and see what they're being fed!
When you get them home/How to introduce myself to them.
It's recommended that you give them a day to settle into their cage once you've brought them home (though I'm usually far too impatient...) just to let them get used to their new surroundings.
After that you can start holding and interacting with them in short bursts and build it up as you and they start to grow in confidence. Most rescue pigs will be well socialised by the time you take them home anyway, but it's always best to give them chance to explore on their own terms for a bit! Hand feeding yummy veggies is a good way to get them to come to you and learn that you=good! Then you can start picking them up and holding them in a blanket if they're timid! I find the best way to do it is to wrap new ones up in a towel/fleece blanket first then I leave it to them as to whether they want to come out of the blanket to say hello to you and get stroked and cuddled!
Hope that helped! Hopefully other members can point you towards some rescues in your area. RSPCA is always worth looking at to see if they have any pigs!
