I have a double axle trailer with hydraulic drum brakes. 1991. The former owners of the unit did nothing to them and they no longer work. No fluid in the master at all. I am looking into replacing the entire unit, coupler, lines and drums. Anyone out there done this before and on a scale of 1-10, 10 being expert, what would you rate the the job as being? I am relatively handy with tools and have plenty of them, but have never performed a brake job on any vehicle.