First off you are going to have to clear the service code in the service mode. Then start by cleaning thermistors of toner. If the codes return you might have to replace thermistors. You may also have to change some of the temperature settings as per service bulletin.
go ahead and replace the 2 thermisters if nothing else looks bad. don't bother cleaning them the code will come back.
also make sure that one or both of the plastic fins holding the heat roller bearings haven't snapped off allowing the bearing to walk out of place, drop the heat roller and pop a thermostat.