Hi Marc,
Take a look at this [http://monitor.espec.ws/files/a610_20a620_185.pdf|parts catalog of a PowerShot A620/A610]. Pages 1, 4, or 5 might help you to find the place for that spring you are mentioning.
The issue with the zoom button might be related to the guide/guideway of the button. Maybe some of the plastic around the button was crushed a bit through the fall and is now hindering the button to find its way back to the end/released position.
Steffen