I would think taking a year off to train for 1 fight, let alone an ameteur fight is a bit excessive. Especially as you already have some relevant skills.
I can't imagine it would be a huge hit, given the amount of insight and "backstage" access we have of top level pro fighters these days. But if you want to do it, then do it.
I just had my first ameteur fight but intend to go as far as I can as a pro. Just doesn't make sense to spend a year training for something that you are only going to do once....