how to install head?
Installing a complete head system is a lot of work, but one an owner can do. Fitting a tank can be a problem as is running hoses in confined spaces. A good source for tanks is: http://www.raritaneng.com/products/holding_tanks/custom_tanks.html.
You need to examine the place you plan to put your tank and try to assess how difficult it will be to work in that area. You want the bottom of the tank completely supported so if the v berth under does not have a flat bottom, you will have to build one. You will probably have to glass in pieces of marine ply to support a tank.
Be sure to buy the very best hose you can find.