2009 Nissan Versa - Slave cylinder and more

Hatchback -S, manual transmission w/ 60k miles: Concentric slave cylinder broke and vehicle was out of service for a year (while I scraped up the cash to fix it). Now the check engine light is on and the mechanic that fixed the clutch says it has something to do with a sensor/vacuum/air something? Had them replace the clutch while it was torn apart. The light was not on before the clutch was replaced. What does the light mean? Did replacing the clutch damage something else that now there is a light where there was none before the repair?

For anyone to provide assistance have the codes read and post them here. Format will be P0123. A store like Autozone will usually read the codes for free.
Your mechanic should have done this and told you what the codes mean.
There is the possibility during the clutch replacement something could have be damaged or dislodged. Or it could just be a coincidence that a problem occurred after the replacement.