I went in for my first oil change at the mini dealer at 7000 miles and after I drove the car it immediately started overheating and the check engine light came on. I am guessing to do the oil change you must disconnect one of the fan belts and the mechanic forgot to reconnect it?

 

Check your coolant tank level, they need to move it to get to the oilfilter. Might be your problem.

 

Fan belt?!!!
Those have not been on cars for about 20 years....
Fans are electric...most have been since the EARLY '80's (most every import I know of...knowing Detroit...maybe '85 or so for them)....

 

Follow up: okay, I checked the coolant tank level and it was low. I filled it up and the engine light went out after a day. I told the dealer about it and they said that low coolant level wouldnt make the check engine light go on. There was also some antifreeze that may have dripped on the engine during the oil change because there was a bit of steam relaeased after I first drove it.