A proper installation is watertight, level, and leaves grab bars anchored into structure, not just tile. Ask how long the crew has installed this specific product, whether they carry insurance, and what the warranty covers on both the tub and the labor.
Get the warranty terms in writing. A long warranty on the shell means little if the seals, pump, or door mechanism — the parts that actually fail — are covered for only a year.
Slide 8 of 9