id think about his quality of life....it wouldnt be much fun stuck in a petshop with no company etc, whearas with you, he could have a shot at a normal life and a home full of love. id think the benefits outweigh the drawbacs. ive had 2 rats neutered, both went fine and both are now much happier rats, and previously they werelone rescue rats i took in, now they all live in a group of 19.get your vet to check him over, and of hes given the all clear, id go for it!
generaly petshop rats have poorer health that their breeder counterparts, but hes only young, so thats with him
introductions with neutered rats go much easier than with entire rats, whether it be male or female, and males should be kept away from females for 2 weeks after the operation to make sure theres no live sperm left to impregnate one of your girlies!
id trust your gut on this one.