A dilemma

SO my boss, the Head of Geography, is leaving after being my boss for 9 years and that raises some interesting issues. I don't know what thoughts the Head has had yet but as there is a need to save money the cheapest thing would be to appoint from within whilst hiring an NQT to teach the lessons. The thought of someone coming on as a Head and re-arranging everything that works nicely is not a pleasant one (why do they feel they have to change things) but the only person in the department who would be interested is me due to either family commitments, illness or having other jobs in the school but I already have 1 new job for next year as well as a full workload as OUP have asked me to write them some exam questions. On the other hand I am buying a new house and extra income is always useful. A decision needs to be made.