Should be easy to repair.
If the corrosion is primarily from salt, wash it in warm water first, salt may not dissolve in alcohol. Let it thoroughly dry then give it the brush and alcohol treatment.
All the components are encased in resin of some type so they have probably survived, the copper tracks on the board may have corroded right through and gone open circuit through. If any have, you can wire across the ends of the tracks to restore the connection, it won't look neat but it does the job.
Brian.