Please help I feel like I'm being lied to and taken advantage of-Bought a used SUV the speedometer doesn't work dealer fixed the mileage went from 160000 to 212000 yet the dealer claims no only160000

I just recently bought a 2003 GMC
Envoy 4 wheel drive SUV with
160,545 miles on the dash from a
private dealer in Massachusetts.
Minutes after owning the SUV I
learned that the speedometer and
the gas gauge was not working.
My dad and I brought the SUV
back to the dealership and said
that it needed to be fixed of
course at first the dealership
didn't want to take care of the
issues but after we explain that
we are aware of our consumer
rights in the used car warranty law
in Massachusetts he could either
do the right thing or we would
take further action so suddenly
they were more than willing to fix
it. Well I just picked up the truck,
the dealer supposably fixed the
issues but now the miles are
showing up as 212,870 instead of
what the dash showed (160545)
when purchased and until they
took truck to fix and the dealer is
saying that for some reason when
they put the part in to fix the
spedometer it jumped the miles
up to the 212000 but the truck is
really only has 160000... IS THIS
EVEN POSSIBLE???                          
I would greatly appreciate any and
all responses THANK YOU!
This truck has been nothing but
an issue since I bought it not even
5 minutes into owning it it broke
down and wouldn't start back up
that's how I learned of the gas
gauge not working, it was out of
gas. As well as a few other issues
and I just would like to know if
their story is possible or not
before I start taking the steps
needed to hopefully get a refund I
don't want a vehicle that has such
high mileage on it 212000 seems
like an awful lot