Steering vibrations in idle and more fuel consumption

Hello,

I own a Chevrolet optra 1.6 Petrol.
Recently I found that there is oil coming in one of the spark plugs, so I gave my car in the garage to change the camshaft gasket.
The guy who replaced the cover said that he had also adjusted the tappet.
Now the car has heavy vibrations in the steering during idling. Pick up is good but fuel economy has reduced to half almost.
I am not sure what he did actually.
Please let me know what to do.

Best Regards,
Yogesh