Help! Plumbing / check valve advice needed stat

[Capt. Obvious]

Our sewer backed (3rd time in the life of the house). Finally got a camera down there and found a busted check valve - it's stuck in the open position so the 4" pipe constricts to maybe an inch.

Plumber gave us a quote of $2600 (insane). The check valve is probably right next to the cleanout - both are in the finished basement a few feet from the foundation. Will need to jackhammer to access and replace the valve.

Just had a second plumber in - said he'd just rip the valve out because he insists we don't need it, and charge us $890.

I'm seduced by the quote but really nervous about ripping the valve out.

We're not at the low point of our subdivision, and our sewer is on gravity but I have no idea what happens to the sewerage once it leaves the subdivision (does it get pumped further down?).

I figure the check valve was probably installed for a reason.

2nd plumber is coming back tomorrow to fix one way or the other.

I don't know what the right call is.