Dripping Delta single handle shower head

The dripping in my shower is about to drive me nuts. In the past 4 years it has been repaired 3 times by a professional plumber for the dripping and the inability for the water to get really hot. The wall on which the controls are mounted can be accessed from behind, so I am ready to cut a hole and replace the entire assembly. Before I do that is there anything that should be checked to make sure the Delta cannot be repaired? How big should the hole be to remove/replace the whole assembly?

A Delta can virtually ALWAYS be repaired, so we would need to see some pictures of your valve to recommend how to proceed.

If you decide to replace it , many of us would recommend a Delta R10000 valve.

Start with approximately a 12" X 12" hole. The hole size can then be refined to faciltate a neat patch.