Skinny Pig---You definetely need to adopt a companion guinea pig for your current one. Not only will it provide the required companionship that all piggies need, but it is also a living breathing, source of
warmth for your skinny pig.
You could look into getting a small animal heater. That's what I did for my hairless rat and my duckling, when I had them. You have to keep it clean, but it's well worth it. This is the one I have: (broken link removed)
Also, you should invest in a polar fleece cavy cozy or two. I believe that the polar fleece is the warmer, more "insulating" of the fleeces. I used this for my hairless rat: (it's not a cozy, but it's an example of polar fleece. Check guineapighome.com for people selling cozies, there are bound to be some that offer polar fleece as a material)
Sleepers & Hideouts for Ferrets, Rats, & Guinea Pigs: Marshall Hanging Ferret Nap Sacks.
You are going to need to get a bag of Oxbow Cavy Cuisine pellets (if your GP is older than 6 months). If a
cavy-savvy veterinarian finds that your cavy is less than 6 months, you need to buy a bag of Oxbow Cavy Performance. 6 months or less needs unlimited pellets, older than 6 months needs only 1/8 to 1/4 cup per piggy per day.
For hay, you are going to need to look for Kleenmama's Hayloft brand (online only at (broken link removed)), or Oxbow. KM's is usually preferred. If your GP is under 6 months, it will need alfalfa hay mixed in with the other type of hay (KM's has timothy [best to get the 3rd cut] and bluegrass, and alfalfa). If over 6 months, it should no longer receive any alfalfa hay, only grass hays. Hay must always be available to your guinea pig, 24/7, unlimited.
As for veggies, go to the diet/nutrition thread on here, and go to the bottom of the first top section (sticky threads), and click on where it says Nutrition charts. Print this out, and always refer back to it and refer back to here. Your guinea pig needs at least 1 cup of leafy greens a day, plus other veggies (non leafy greens, as per the nutrition charts). Fruits are to be limited to once or even twice weekly. However, since your piggy has very likely never eaten veggies before, you will need to introduce them slowly.
Start with any type of lettuce (except for iceburg). Offer a few small pieces, along with a few small pieces of green or yellow bell pepper. Leave it all in the cage until the lettuce starts to wilt. You may have to do this for several weeks until your piggie begins to eat, but then again, your piggie might just dive right in! You could also try eating some of the lettuce and bell pepper in front of your piggie, if you have to.
Well, best of luck to you. Hope I could help some!