I more or less went the same route. I also added an electronic insulation transformer, a new Alpha Pro II alternator controller and an AC monitor. You do not need the service tech password for adjusting any of the charging/voltage parameters. The service tech password is mainly used to adjust the calibration of the various devices. But you can really mess up the system as well with it. If you really need it I can provide it to you .
You typically do not replace the actual busbars, but you put the Mastershunt as the very first device between the batteries and all the rest.
Please do remember that what you wrote down in three or four sentences is in reality a week of work. Ask me how I know.