Replacing Shower Valve

[Justin Case]

Basic tub/shower spigot starting dripping when off. Had to hire plumber to help replace handle cartridge. Mid 80's model and very tedious to fix. Took plumber 2 hours. Cost $300. Called around and this seemed normal.

New tenant is still complaining the water is dripping when turned off.

My next option is to replace the shower valve behind the wall. Behind the wall is the mirror footprint of the other duplex ie the other tub/shower. The tub/shower is the basic one piece shower tub shroud. So will need to get behind this to replace shower valve.

Any one have estimated cost for this?

So far got two quotes:
$2,300 and $1500+tax.

Thanks