No one could tell you of thats a good deal or not without looking at it, or understanding the scope of work.
To go into a finished home and rip into walls, ceilings, floors etc... Fish pex tubing throughout, remove all old galvanized, put new valves on every faucet etc.. It's going to be expensive. As an example.. A quarter turn 1/2 to 3/8 standard valve for under a kitchen sink to hook up your faucet, you'll need 2 of them. They cost about $9 each. Every fitting, joint, tee, etc runs $2-$5.
What I'm getting at is plumbing is costly, plus the time to navigate existing built home. I can tell you it won't be easy.
Go out and get 3 more bids, then you'll know what a good price is. Normally they bids should be fairly close to each other.
I recently got 4 bids on a new driveway I wanted. All 3 came in at about $1400, one of them was $2200.
Hope this helps.