Resetting the odometer in a TR

I have managed, after 5 year of ownership, to break the Odometer in my 91 UK spec TR , seemingly by resetting the trip whilst moving. This was the first time ever I have even tried to reset the trip, however, according to the handbook ( which I read later) this was a task that I should have undertaken whilst the car was stationary and the trip knob turned clockwise direction only, certainly news to me and others to whom I have spoken. Speedo and Tach all working. b.t.w.
So notwithstanding all that, it has stopped working. Twiddling the knob (this time in a clockwise direction) doesn't work and I am not sure what parts, if any, were damaged, but i would hazard a guess its likely to be the mechanical internal gear bits, which I understand from other Threads on this forum are nigh impossible to find. Accordingly I have sourced a refurbished unit with the view to swapping it out and maybe if the old unit can be fixed and maybe swapping it back in.

There are two questions i would like an answer to if possible: ( i have searched the forums already)

First: Before I get the old unit out, is there any thing else the forum can suggest I can do to the unit whilst in situ to try and get it working ?
Secondly, if I do go ahead and install the refurbished item, it is inconveniently is set at 4 miles (see photo).
I would like to set it to the current mileage 24,000ish Reasoning that I do not want to have to explain why the recorded mileage on the ODO differs from the actual mileage on the service records, should I ever wish to sell the car. Also, in the UK if you change an ODO then at the car's next annual MOT the recorded mileage is set to the reading of the ODO in the car and a note is made on the record. Is there an easy way to do that i.e driving the small motor in some way or is it having to manually turn the worm gear or heaven forbid taking the dial off and manipulating them physically. (not, as my mate helpfully suggested, by painting white numbers on the dial with tipex)

Thanking you all from the UK

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