You are looking at 2 to 3 hours to pull the engine out & put it back in
Then another 2 hours to pull the engine apart replace the governor & reassemble the engine
Plus another hour for cleaning, tuning & testing
So all up about 6 hours labour + parts
If you got charged 8 to 10 hours it would not be unreasonable.
It all depends upon how easy things like the drive pulleys come off
I have worked on engines that took a full 10 hour day just to get the PTO clutch off.
I charge scheduled fees to allow for lack of specific tooling , hoist & lack of factory training.
However scheduled fees assume you are doing warranty work on a nice new clean engine so everything comes apart easy.
Some engines are so messy it takes several hours just to clean them enough to be able to split them apart.
A gasket kit & seals is not cheap either.
It also depends upon what they find inside the engine.
If a weight has just fallen off the pin on one side then it is pull it out and drop the new one in.
If it has broken up into tiny bits then you really have to remove everything flush & degrease filtering all of the liquids till you can account for all the little bits of metal and that can take a lot of hours.
Then of course there is the hourly rate charge
I charge $ 60 / hr the shop up the road who owns the land charges $ 90/hr the big showroom shop in town who rents charges $ 150 /hr