Try a new fuse in the plug (if you live in a country that has such marvelous things of course)
If it isn't the fuse, think about buying a new microwave - new ones are very cheap these days, and very likely cheaper than the hourly rate of an electrician plus the replacement part cost - if he can get it.
Even better, use the experience as an excuse to ditch microwave cooking of junk (convenience) food like I have recently. Microwaves destroy the nutritional content and texture of food. It's actually cheaper to buy fresh ingredients and gently steam them in their own juices in a pan for a far healthier, more tasy meal. And it takes less time than you think too. Why not try it for a month before shelling out on a new microwave - might be the best thing you do all year.
Mr Big, January 2007