by 'done' I assume you mean neutering? If so, then a boar being neutered makes absolutely no difference to their ability to get on, neutering doesn't change guinea pigs behaviour like it does for other animals - its character compatibility which is vital. all neutering does is prevent pregnancy. two boars do not need to be neutered to live together and your boar won't have any idea if the other boar is neutered as they will both behave absolutely the same.
character compatibility and mutual liking is the key to a successful bond - the two piggies have to like each other to be able to form a functioning hierarchy. the best way to find a character compatible friend is to go dating at a rescue centre. that way, your piggy chooses his own friend which will result in a good bond. the rescue centre will help with the bonding procedure and you'll know the piggy you are bringing home is healthy as well as being assured they like each other.
if you buy a piggy on spec from a pet shop for example, then you will have no idea if they will be compatible and like each other, so you need to have a back up plan if they don't by having a separate cage so they can live side by side as neighbours with interaction through the bars to stop loneliness. You also have to follow the bonding procedure correctly - you cant just put two piggies together. You also need to forego quarantine if any piggy you bring home is less than four months old (babies need immediate bonding with an older piggy) so you do run the risk of bringing in an illness but in that case you'd just have to be prepared to treat them both.