A first visit usually covers the size of the room, the direction of the floor joists, where the drain can go, and how the shower will be vented. In a Carver house on a well, a careful remodeler or their plumber will also ask how the water system performs today, because a new shower that starves for flow is a common disappointment.
Paperwork in Carver is in person. The Building Department doesn't offer online permits, so applications are printed and brought to Town Hall. Expect a plumbing permit for the valve and drain, an electrical permit if lighting or the fan changes, and a building permit for framing work, which the town says may take up to 30 days to process.
Before tile, ask that the shower pan or membrane be flood-tested by holding water in it long enough to prove it's tight. Once tile is set, a leak becomes a demolition job, so that wait is worth it.