I don't know how handy you are, but I've found e-spares very good in the past at explaining how to do it yourself. In any case, it is worth having a look so that you understand what the repair man is doing. This video is mainly about leaks, but it mentions heaters too:http://www.espares.co.uk/advice/3/2083/how-to-diagnose-dishwasher-leaking-and-heating-problems
I've replaced a soap dispenser, a door catch, and a flow through heater in the past successfully using their advice and they supply parts too.
There are loads of videos showing you how to do repairs to kitchen appliances, and I've used them a lot to keep ours going. Good luck anyway. Well worth an hour's study whether you do it yourself or not.