Fujifilm Finepix F50 fd 'zoom error'?

Depends on the amount of damage to the lens. Fuji will fix it by just replacing the lens unit then re calibrating the camera to the new lens. You may also get warranty on your refurbished camera. It does sound quite a lot of money to get it repaired considering you could just buy a new one for the same money.
Common damage to the lens from dropping is the plastic guide ring inside the lens. This guide stablizes the lens and prevents the end piece from rotating and also guides the focus lens inside as you zoom the lens.

Dave - Camera repairs
March 2010