Most Rockland hall bath projects keep the plumbing roughly where it is. A remodeler will check the tub drain and toilet flange, the condition of the subfloor, and how the existing fan is ducted, then suggest changes that work within the footprint.
The building permit application can be filed online, and the plumbing, gas, and wiring inspectors are part of the Building Department. Each trade pulls its own permit, and inspections happen in order: rough plumbing and wiring, then close-in, then final.
If your project only replaces fixtures in an existing bathroom, it shouldn't involve a new sewer connection. The Sewer Commission's moratorium on new connections, in effect since March 12, 2024, mainly matters if a property isn't yet tied into town sewer, so ask the Sewer Department if you're unsure.