hi I know a lot about guinea pigs....
1) Find out the sex of your pig and if it's male find out if it has been neutered (though you'd be able to see if it hadn't?!)
2) If it's a boar and not neutered, find a competent vet to do this as it can be a nightmare if it goes wrong. (The only vet I recommend to do it is in Reading..Tilehurst vets... they used to be experts in guinea pig care... and probably still are as there is a good community of guinea pig lovers in Tilehurst!)
3) Then you need to find your guinea pig a guinea pig friend... they cannot live alone as they are social animals. DO NOT pair them up with a rabbit!! This is really awful and I've heard terrible tales of the injuries rabbits cause to GPs. They are not the same at all and rabbits can be over-sexed and cause horrific internal damage to a GP, plus they kick. A guinea has to be with another guinea. This can be tricky as males do not take well to living with other males and almost always end up fighting in the end (unless they've been brought up with each other from a young age). So... neutered boars need to live with a sow, and sows can live with another sow or a boar. Don't just go and get another guinea pig and expect them to get on... ideally you should present your pig with two different pigs to see which one they like the best. Some rescue centres may be happy to do this with you.
4) They need a BIG hutch. 1 - 2 pigs need a hutch 120cm by 60cm. Anything smaller is cruel really. And a safe fox-proof run on grass ideally, failing that then a good safe space to run about indoors out of the hutch (this is the best bit about pigs as they can be hilarious once left to roam free-ish).
5) they need a constant supply of good hay - not the rubbish you get as bedding but good Timonthy Hay or other speciality hay. There's a great website: [www.thehayexperts.co.uk
]. But this is possibly more important than anything else - hay all of the time (alongside fresh veg, bit of fresh grass but not too much, water and uncoloured pellets)
6) they need guinea-pig friendly... NOT SAWDUST.. this gives them breathing problems.
7) And they need to live indoors in winter - they can't cope with UK winters. Mine came in to the kitchen for 4 months of the year and would get very excited at Christmas dinner.
They do need special care really as they get an awful lot of things wrong with them otherwise.
Here are some good resources for you:
Enjoy them - they are great animals.