Incorrect Valve Adjustment Fallout...

I recently had my 90k service performed on my Honda Civic EX 2000 at a
Firestone Complete Auto Care. This included spark plug replacement,
ignition wires replacement, fuel system tune up, valve adjustment, etc.
As soon as I left with my car I noticed something was definitely wrong
with my Honda. The RPMs were sporadic and would go to just above
bottoming out at the first stop light I reached. I was concerned about
the vibrations but thought it would subside and the RPMs would return
to normal levels, but is only continued and became more frequent. After
a month I brought my car back to Firestone to explain the problems I
was experiencing and they said that the car checked out and there was
nothing they can do without an engine light coming on. The vibrations
only got worse and within a week a check engine light went on. I
brought the car back again and Firestone finally took my car to a Honda
dealership, which had to re-due the value adjustment because it was out
of spec. They also said the O2 sensor error was showing up and that is
why the check engine light came on. I have never had a problem with my
Honda before and none of these problems existed before the 90k service
was performed.

I need to know if the O2 error could be contributed to the incorrect
vale adjustment (excess vibrations) and if there is anything else I
should be looking out for because of the incorrect work.

I would greatly appreciate any help.

Ben Jones