The number one quality you should look for is trust. Off course quality in the work performed is important, but that you can trust your point of contact is key to succeed.
Make sure you find a storage that is certified Service Partner for your engine manufacturer. Goldfish Service can be of assistance if you need help. Most manufacturers have a web solution for locating you nearby service point.
Tell your storage that they can contact Goldfish Service for any questions. We are keen on helping out in any way we can to make your ownership easier.