If you want to make ammonium acetate, then all you would have to do is mix a solution of ammonium hydroxide and a solution of acetic acid, then evaporate to get the ammonium acetate. The only problem is, if you need it anhydrous, then that way just won't do. In order to get rid of the water, then you would have to heat it, but the problem is, when you heat the ammonium acetate up high enough to drive off the water, then it will dehydrate into acetamide. So you have to use anhydrous ammonia and glacial acetic acid. So just bubble your ammonia gas into your glacial acetic acid. I don't know how soluble ammonium acetate is in GAA, so it might even immediately precipitate from the solution. But even if it doesn't you won't use up all of the GAA because if you did, then you would end up with a solid chunk of ammonium acetate. So just bubble it until it becomes really viscous, or until it becomes too thick with precipitate to work with, then just evap off the excess GAA.
Oh and don't forget, the GAA+NH3 reaction might get a little hot, so you might use an ice bath.