It is likely one of
these have blown they are what make the dryer warm. There may be a safety device which will trip if some one does not clean the lint catcher or if the exhaust gets blocked.
As to changing not my thing and I would have to do one to find out how it is done and from past experience when one thing goes unless due to poor maintenance of fluff filter it is not long before some thing else goes so I would only both with a fairly new machine.