Pulling out a tub and building a walk-in shower is the single most common bathroom request we get, from aging-in-place remodels in Cave Spring to rental refreshes in Blacksburg. It's a great project. It also fails quietly when it's rushed, and you don't find out until the ceiling below stains.
The pan and the walls are the whole job. A proper shower is waterproofed as a system, with the pan sloped to the drain, the membrane turned up the walls, and the corners and niche sealed before a single tile goes on. Tile and grout are decorative. Waterproofing is what keeps the water in.
Valve depth is where a lot of DIY and bargain conversions go wrong. The mixing valve has to be set for the finished wall thickness, tile and backer included, or the trim plate never sits right and the handle sticks out or sinks in. It's a plumbing decision made before the walls close, which is why our plumber and tile setter are on the same crew.
Ventilation matters more in a shower than a tub. A properly sized exhaust fan, ducted to the outside and not into the attic, keeps the bathroom from growing mold on the ceiling six months in.
Plan the details for how you'll use it: a bench, a hand shower, grab bars blocked into the wall now even if you don't install them yet, and a curb height or curbless entry that suits everyone in the house. Done right, it's a room you never think about again, which is exactly what a bathroom should be.