Two very different jobs answer to the same question. Swapping one cracked panel in a sound frame is glass, a measure and a set. Stripping a failed enclosure and starting over is demolition, disposal, new hardware and new anchors. Which one you have decides the number, along with panel size, thickness and the state of the tile.
Glass fails more often than the metal around it. A panel can be cracked, chipped at an edge, or etched cloudy by years of hard water while the hinges, the channel and the header are still solid. In that case the work is measuring what is there, matching thickness and any pattern, fabricating a replacement with the holes in exactly the same places, and setting it. Nothing gets demolished and the tile is never touched.
Matching decides whether that route stays open. Hardware finishes and glass patterns change over the years, and an older combination may no longer be made. That question gets answered at the measure, before anybody promises anything.
Rollers worn oval, hinges with play in them, a corroded channel, or a header pulling away from the wall all say the assembly has reached the end of its service life. New glass hung on tired metal simply moves the failure a little further out. When a fitter recommends replacing the whole enclosure, this is usually the reason, and it is fair to ask them to show you the part that is worn.
Age of the design is the other thing to weigh. When a unit is old enough that its hardware is out of production, one replacement panel today probably means a full enclosure the next time anything else lets go. Putting new glass into a system nobody can supply parts for is a choice worth making with open eyes rather than by default.
Most replacements drop back into the opening you already have. The curb, the tile and the plumbing stay put, and the new enclosure is cut to that opening rather than the opening being altered to suit a stock size. Where a new layout wants an anchor somewhere different, that gets planned at the measure so the holes land in solid backing. Taking the old unit out and disposing of it is part of the work, and our own crew handles both ends.
Style can change even when the opening does not. Plenty of these jobs are a framed unit coming out and a frameless or semi-frameless enclosure going into the same space, which shifts glass thickness and hardware and moves the number accordingly. The cost guide compares those styles, and a free in-home measure turns your specific opening into a firm figure.
Usually, yes. An enclosure is measured to the opening you already have, so tile, curb and pan stay where they are. Re-tiling only enters the picture when the tile is already cracked or when water has been getting behind it, which a measure picks up. A new anchor position may want a hole drilled, not a wall rebuilt.
It comes out and leaves with the crew. Tempered glass is taken down in one piece where possible and handled carefully, since a chipped edge can let go without warning. Old anchors are pulled and the holes are dealt with before new panels go in, so the finished wall does not carry the previous installation's mistakes.
Forty years of North Jersey bathrooms says the answer depends on what sits behind the glass, not on how the glass looks. Send a photo of the enclosure and of the damage, and you will get an honest read on whether this is a panel or a project.