I have some water damage due to cracks where the Dome transitions into the flanges. I didn't realize it until water dripped on my head while I was taking a shower. The water was running down the roof framing and then wicked its way on top of the ceiling paneling spreading out.
You really need to go ahead and replace it now while you can before you have a lot of water damage and have to start tearing into the roof. A temporary fix would be to put some Eternal Bond over the cracks. That would have least stop any possible water from getting through if it hasn't been already.