At that age only the vet can castrate, under full anaesthetic. Will create an open wound etc. Not sure if the male smell will disappear though, as all of mine are done with rubber ring before 7 days of age.
I wouldn't take an adult male (probably very set in his ways!) even if offered free! Also you would need at least two goats (and only a young (clearly smaller) wether or a friend (and not a rival!) from his previous set-up would be acceptable to him - otherwise lots of fights). I am not sure how he would react to females after castration?
Doesn't sound like a good idea all round!