Yes fixing up bikes can be done on the cheap here.
It sounds like you need a new speedo panel, Easy enough to get via Lazada or Ali Express. Check the drive unit in the front wheel first... Maybe that's the problem, again it's an easy fix/replacement part.
I did up a disused scooter for around 2500 baht. Parts replaced included:
Front / rear tyres and tubes
Front caliper and pads
Rear brake shoes
Front forks
Light cluster, changed all lights to led
Carburettor
Brakes levers
Battery
I'd hate to think what that would cost in the West.
Some real bargains to be made if you can fix things up yourself.