MAF sensor replaced at dealer and the idle still fluctuates along with the car bucking when going into reverse and drive.

The other day my car began idling erratically, jumping between 1000 and 2000 rpm
while idling, the check engine light came on and then the car shut off. My car started up
after a few moments and I was able to get home but the rpm at an idle still jumped up
and down.
Next morning I took my car to the Chevy dealership. The idle no longer jumped up and
down but now idled around 1700 rpms upon start up.
I was told that I needed a new MAF sensor and told them to go ahead and change it. I
picked up my car just before they closed. It seemed fine for about a block and then the
idle began fluctuating again along with the car lurching when being put into drive and
reverse.
I tried disconnecting the battery for ~15 miin and starting the car with the parking break
on. Let her set and then the idle dropped down to 1000 rpm where it stayed. When to
test drive around the block and immediately experienced the lurching when shifting into
drive and reverse, then the idle actually dropped below 1000 rpm. When I tried to rev
the engine the rpm's would kick back as soon as they got up to 3500 rpm.

I feel like the dealer misdiagnosed my vehicle and I paid for a part that was probably
working properly. Any ideas on what could be causing my car to behave this way? Did I
just pay $500 for a part that I did not need?