vw 2001 passat wagon v6 137k miles

just had a tune up and spark plugs and wires replaced last week. i picked up the car
from the vw dealer who did the work and lo and behold later that day the check engine
light came on and has been on since then? i'm wondering if they failed to properly
secure the wires or if they did something wrong in fixing what they were supposed to.
at time of service also suggested new valve gasket covers. couldn't afford to do it all
at once.  spark plugs seemed the priority at the time.
car is old, lots of miles and i need it thus the reason for sinking money into it.

could check engine light be related to the spark plug/wires being recently replaced or
not replaced correctly. OR is it a separate issue altogether.

any input or advice would be much appreciated. thank you!