Adam if its any help I have probably got the full honda workshop manual for your outboard if its a relativley new 4 stroke (post 1999) and could print you a copy and send to you, just let me know the model and year. Doing the replacment of the head isnt actualy that scary a job if youve got a decent set of plans, a bit of time and half an idea how it all works its not beyond anyone with a bit of mechanical ability. Sourcing a second hand head or having the origional repaired will be the hard bit, assuming you sort this its just a case of strip down and replace using new gaskets followed by a full flush to make sure you get rid of any salt water left in the crankcase. Good luck.