Permit to replace a toilet???

I'm attempting to do a bathroom remodel, and trying to doing all my due diligence.

it's an exceptionally small bathroom, 6'9 x 4'11, and it's the only one in the house. My wife is adamant about using a contractor, neither of us are experienced with this kind of work, even though I think we could manage with help from knowledgeable friends.

We plan on demoing the whole room and installing new fixtures and transitioning the bathtub to a walk-in shower.

Some contractors I've spoken to say we don't need permits, some do. On top of that my city is giving conflicting information. #1 their website is trash and attempting to find anything specific as a homeowner is impossible. My wife called and spoke with someone that told her any fixture change including just a toilet would need a permit. I do think we'll need a permit for bathtub/shower but needing a permit for a sink or toilet sound insane to me.

I'm pretty lost on knowing where to go to find the correct information.