Vectra in garage?

Our 2005 vectra broke down recently. The maintenance and battery lights both came on and the car wouldn't start. AA said alternator went. Had this changed at garage and the car broke down while they test drove it. They took it back, had a look again and said the cambelt kept 'leaping'. They have looked inside the engine and said 2 fillers (not sure if I have understood them right) or valves have become lose and they need to order 2 more at £40 each.

I am looking for reassurance that this is going to cure the problem. I am so worried about losing my car but they have said it can be fixed. Any advice would be great.