How can I fix my Hoover Nextra 7 (HNF7167-80), as it will not drain?

My Hoover Nextra 7 (HNF7167-80) won't drain. There isn't a blockage in any of the pipework & I think that either the pump's packed up or (heaven forbid) it's the motherboard. Is it possible to tell which one it is without the expense of calling out an engineer? And if it is the pump, is this something that can be fitted by a very competent son?