My son had an undescended testicle which needed an operation when he was about 13 or 14 months from memory. He had a small incision in his lower tummy where they went in to find the teste, they pulled it down and put it in place in the sack and used a few stitches to hold it there. We were in hospital for the morning and discharged in the afternoon with pamol to give him. he was dopey for that day but the next day was climbing the stairs like nothing had happened. The hardest part was not letting him eat anything from the night before til after his surgery!
HTH