I get a message that says service due in 12 days, what happens after the 12 days if I don't go? Can I reset the light? What service is it?

 

What's your mileage? When was your last service? If you do nothing, light just stays on. Dealer (or Durametric) can reset. From your owner's manual (somewhere around page 127):

Service in km/days Service indicator

Bring the vehicle in for service no later than after
the distance/time shown has elapsed.
However, it is the intervals in the “Guarantee
and Maintenance” booklet that are decisive.

 

Why wouldn't you have the indicated service performed?

 

That's his question - message doesn't say which service and he doesn't know.

 

10k miles just bought it don't know when last service was performed. Can I reset it myself?

 

Yes if you have a Durametric otherwise dealer can reset.