That doesnt sound good

Id take the clocks panel out and check it carefully for shorts etc.

That may go up in flames taking your car with it.

You may need to replace the panel, in which case I would take photos of the mileometer, with a dated newspaper in the picture, then do the same with a new, 2nd hand panel to try and help prove any mileage descrepancy in the future.

use the maintenance guide index, either in my sig, or at the top of the maint guide section,

there is a guide on doing this 

Place a "wanted" ad in "test" section and one of the mods will kindly move it to relevant section