Are you in the UK? You mention that it is 'H' reg.
If so that puts it registered between August 1968 and end of July 1969. It makes no difference as it would still be a 'dry-braked' tractor.
Before any stripping you should ensure that both sides are adjusted correctly and the operating arms move freely. Are the adjuster nuts free and the bushes inside the arms free?
Usually if the rod coming out of the actuator housing is close to the back of the footplate bracket it will mean that the discs are worn out.
Remove any cab and preferably the wing (fender) on each side. Support the tractor under the centre and remove the wheel. Disconnect brake rods and wiring. Use a substantial trolley jack or lifting tackle to remove the axle. It's heavy so make sure that the lift keeps it in balance.
Inside you will see the inner bearing plate retained by two screws. Remove the screws and remove the plate. This will give access to the actuator and discs and seals. If the brakes are worn or show any signs of 'grabbing' it is always advisable to replace the actuators. They are quite expensive. This is the weakness with this type of 'dry' brake. Renew gaskets and reassemble. Please come back if you need any more help.
DavidP, South Wales