Mercedes "Check Engine" light came on:(. Help!?

Okay so not even 5 days ago, I picked up my Mercedes from the dealership here in Austin from getting it serviced and the bill came to be a whopping $1,200! I had to have the contact plate in the transmission replaced on my 2006 C230. It runs great & I no longer have any problems. So today I was driving & the "Check Engine" light came on out of no where! I didn't notice anything that was wrong with the way it has been driving, so what could it be!? What should I do, call the dealership & tell them about it. Or just let it go, cuz it might be something minor? Any advice here is greatly appreciated! Thank y'all so much!:)