But I know tha rabbits are social animals and am worried that my other rabbit should have company (only 8 months old). He has a very large run that he has constant access to so he's not shut in a hutch at all. He's next to the chickens so he can see them through the fence.
Main problem is that he's not neutered so would have to get that done first. Expense and I worry that he'd die in the op. Then I would have the problem of trying to bond him to another rabbit.
tricky, if you socialise with him and handle him regularly he may be ok with just you and the dcs for company. you could consider having him in the house with you occassionally. though you may have to get him neutered anyway as some males can become territorial and therefore become aggressive too. it is far safer to get a male neutered than a female rabbit.
How big is he? A small rabbit can sometimes do well with a couple of guinea pigs for company - you have to monitor closely to check no bullying when they're first together, but it may be a solution for you.
I had the devil of a time trying to find a friend for my rabbit. Ended up building two side-by-side runs so they had a big wire wall to socialise through, but couldn't actually kill each other when my back was turned.
I think people used to chuck them together willy nilly and it didn't always work by any stretch, so now the general advice is against. It can work though - I had a rabbit and a guinea who lived together very happily - used to groom each other and sleep together. They need enough space, and hidey holes for the guinea.
Someone who knows more about it will be able to tell you more than I can - I only know what I've learned from my own pets.
So sorry your other rabbit died. Personally I wouldn't put a guinea pig and rabbit together, especially if rabbit is un-neutered as it will likely sexually harrass the poor guinea pig. Un-neutered male rabbits are more likely to display aggression and spray urine everywhere which is unpleasant. Neutering a male is a cheap low risk procedure, the rabbit will need to be kept indoors overnight, as after a GA they are unable to regulate body temperature. You will end up with a happier rabbit you will most likely be able to easily bond with a neutered female. Visit your nearest rabbit rescue, they usually neuter all rabbits and will keep the rabbit for a couple of days to do the bonding for you. There is a website called rabbit rehome which will direct you to the local animal shelters. Rabbits are very sociable animals who tend towards depression without a partner. The only rabbits you could keep single are permanent house rabbits (with daily human company, although many people feel this is not a good enough substitute for the rabbit's own kind) or those who continually display aggression to others (your rabbit has lived happily with another so shouldn't fall into the latter category). Good luck with whatever you decide to do.
Neutering is far less risky than it used to be - anaesthesia in small furries has really come on in the last few years. A neutered buck will probably get on best with a doe, as the above poster said. Please don't keep rabbits and guineas together either - they have different nutritional requirements and can fight horribly. Guineas also need more warmth, especially at night.
if you haven't got your rabbit a companion yet please do. At 8 months he should take fairly easily to a female rabbit and if you get one from the RSPCA they will already be neutered - although they will want your male rabbit done too. Bonding can be easy or really hard but you do need neutral territory to introduce them and to have them sleep in separate hutches at first.
neutering is a very low risk operation and as he is still only 8 months old he is young enough to bond. It may be different if he were really old, but as it is, spending the rest of his life on his own really isn't good.