How can I make my delonghi cooker heat up a bit quicker?

Delonghi DFS 901SS professional cooker worked fine for several years but now takes forever to reach operating temperature. gets there in the end and the thermostat seems to be ok, so assuming it's lack of power to heating elements, but I've no idea how to get into them.
Any suggestions would be welcome, as would a 'workshop manual' of the internals of the cooker. Are they available over the web?