You should be able to get a liner for about $1500.
So, whatever you're quoted above $1500 is going to be labour.
It only takes a few hours to install and another hour or so
to do the skimmer cutout and the return cutouts
after the water is within 6 inches or so of the openings.
As mentioned YouTube should be helpful.
Of course, there are various thicknesses of liner.
I think you would want the thickest. I think it's 30 mm.

Do you have a vermiculite bottom, or is it sand?