The dishwasher itself is the smallest part of most install visits. The work is in the space around it. When you plan a replacement, walk the spot before you choose a model, and write down what you see. Those notes decide how much of the visit goes to the job and how much goes to surprises.
The opening and the cabinet
Measure the opening under the counter, the height to the floor, and the depth to the back wall. Check whether the floor is level and solid where the feet will sit. A cabinet that has swelled, or a subfloor that gives underfoot, adds work before the new unit goes in. Look at the sides of the opening too. Trim, panels, and the lip of the cabinet frame can need adjusting.
Water in and water out
Look at the supply line and the drain route. Note what fitting the supply uses, where the shutoff sits, and whether the drain connects to the sink tailpiece, a garbage disposal inlet, or a separate branch. Each of those changes the parts list. A disposal that is being replaced or added at the same time pulls the drain connection into the same visit.
The circuit and the outlet
Find out what the outlet is, where it sits, and what circuit feeds it. Some installs use an existing outlet, and some need a new circuit or a relocated box. Ask the electrician to confirm the route before the day of the install, not on it.
Removal and the old unit
Ask who hauls away the old machine and how it leaves the house. A narrow hallway, a stair landing, or a tight corner can make removal slower than the install itself. Note that route on the same walk-around.
What to ask for in writing
Ask the written estimate to list each connection it covers: supply, drain, electrical, cabinet work, removal, and any item it does not include. A line that says the install is included, with no detail, leaves the other lines to be argued later. Compare two written estimates by their lines, not by their totals alone.
The published figures for each system live in the site's own tables. Use them to plan the timing, and use the written estimate for the job itself. The dishwasher page is here: Dishwasher: typical service life and when to plan.