Usually, stripped gears are about the only thing to happen as a result of a crash.

If a crash is the result of a possible failed servo, it gets a little more complicated.

Check for stripped gears first.
Tap on the servo sharply on all sides and watch for movement or jitter.
Checking for frayed wires at the board, wiggle and jiggle the wires going in to see if it affects the movement or position.
Check the connector end for corrosion, bent pins, loose fit or frayed wires.
Apply a resistance to the servo arm with your fingers while someone moves the stick slowly through it's full range of travel.
If you see, hear or feel any change in pressure as you go, it may have a worn pot.
If it has a lot of time on it and it jitters at center but is good everywhere else, it may need a pot.
If it fails any test, don't use it.
If it is an expensive servo, send it in for repair describing the problem.
It usually doesn't cost too much for repairs.

Kirk