If they are not leaking, I'd use the housing during your season. Some superficial corrosion occurs often, especially if the rinse of salt water is not perfect. The real problem is if they leak, not the cosmetic appearance. They can leak due to corrosion or salt build-up on the pushrods, or worn O-rings. O-rings you can replace. Salt build up can be removed with a vinegar soak. If they pushrods are corroded so they are rough or smaller, then they really should be replaced.
When you do remove the pushrods, be very very very careful to shield the E rings from flying away, which they do very easily. They are stainless steel and hard to find locally. Lose one and it will have to go to Ikelite.
Personally, I would buy the spare parts and replace any O-rings that were leaking. The O-rings do wear out and salt builds up on the push rods, so eventually they need attention. Some silicone spray on the pushrods will help with sticking. When you can spare it, you could send it to Ikelite and they will do needed maintenance. If more than about 3-4 buttons are stiff or corroded, then they all should be replaced but that's a judgement call.
