My 3 1/2 year old sow fell for the charms of a 12 months old boy (out of a choice of three neutered boars at the rescue) and lived happily with him for the remainder of her life. Llewelyn, now at 3 years old has a harem of girls aged between 6-16 months. On the weekend, a four year old lady is going to join the tribe; she has shown that she can get on with boars and groups at the rescue she was handed in.
Age difference is not as important in cross gender pairings as it is with boar pairings, as dominance is not a real factor.
If you can, ask around for a rescue that has several girls, so Peanut can chose his own girlie once he is safely neutered. Otherwise, talk to the rescues and they might propose a suitable girl. If she joins you before the end of the six week recovery period, it helps if you can keep them next door to each other, so they can become friends through the bars.
While it is quite safe after four weeks, "golden shots" have happened at five weeks after neutering, which is why a six week period is generally recommended on here and observed by most rescues.
Here is a link to find rescues near you:
http://www.guineapigrehome.org.uk
I send my best wishes to Peanut and hope that he makes through the op and recovers quickly from his ordeal!
