Electric cookers?

Hi, I have a Neff U1722 double oven. Bottom oven fan had been making a labouring sound for a couple of weeks and then stopped working. Immediately, this seemed to cause the bottom oven to stop heating up, rendering it unusable. The top oven still works fine and the clock is still operating. We would like to try to fix the problem, but don't know whether to replace the fan or heating element (don't want to purchase both if only one of them needs replacing). Can you help please?