Dave,
It will be around a month's work for who ever you subbed it out to. You will be surprised at the amount of paperwork involved. Then when revisited the manual will need rewriting every year after the audit is done.
You have to do an internal audit and then external once a year. A lot of hassle , that is why it is a highly acknowledged accreditation.
For a small business your size it will be an awful lot of money to invest. This was one of my major pet hates when working in industry but is good to keep your house in order.