[Roadsters] Tandem brake mastercylinder rebuidl

[Arthur]

I recently purchased rebuild Kit for my 68 2000 ,
this car already had had one replaced a few years ago
I seem to remember changing seals and piston on an English Truck from inside
the Vehicile but that was 38 years ago is that possible  on a Datsun?
or am I being too lazy ?
I am getting the car ready for resell so want every thing safe and sound