The things people actually worry about
How long will I be without water?
Generally during working hours rather than around the clock, with water restored overnight where the stage of work allows it. A realistic day by day picture is part of the plan you should get before booking.
Will my house be full of holes?
There will be access openings, and the survey should tell you roughly how many and where before you commit. What matters is whether patching, texture and paint are inside your quote. Get that in writing.
PEX or copper?
PEX is the common choice for valley repipes and it performs well. Copper is still available and costs more. The real answer depends on your house and your preference, and you should hear the trade offs rather than a house policy.
Can I do it a section at a time?
Sometimes, and for a large house on a budget that is a legitimate plan. It costs more in total because setup and access happen twice, and it leaves old pipe in service in the meantime. Worth discussing honestly rather than dismissing.