System retrofit - Southern California

I’m looking for input on a retrofit quote I received for my home. I know nothing about irrigation other than my system doesn’t work very well - think the prior owner did some of it DIY.

Here’s the scope:

•	Replace 120 heads — 4” Rain Bird popups, swingjoints, nozzles, shrub heads, & filters  
•	10 Irritrol complete valves — rebuild manifolds  
•	Install 1” ball valve and brass double union regulator  
•	18 sprinkler heads add or move — 1 garden valve

Appreciate any input on what a reasonable cost for this is!
Thanks