How do I reaffix the blade assembly in my Flymo RCV340?

The whole blade assembly has fallen out of my Flymo roller compact 340. There are three ball bearings and a crimped metal washer. Then there is the blade which is attached to a circular bit with spaced verticals.
It looks as though it should just push back in, but I don't know where the washer and ball bearings go! Can I fix it, or does it need a professional? Do I need to buy new parts?