2001 mazda idling problem

I took my 2001 Mazda 626 (2.0L manual transmission) in for a normal presummer maitenance (I live in Montreal so it is still presummer): oil change, air filter change, air conditioning system check and change of radiator coolant.

When I got the car back I had this problem with my idling. It basically oscillates between 1K and 2k and the whole car shakes. After watching this for 20 minutes the check engine light went on and remained on. I have figured one way to get my idle under control and that is to turn on the front window defroster with the full fan. The only problem I had going in was that the car was sluggish when shifting between first and second gear. This happened when the car was not fully warmed up. Any ideas as to what is causing the faulty idling and did the garage do something wrong or is this just circumstantial. My boring family car sounds as if it wants to be let out of the cage!!!

clean the throttle body.check for vaccum leaks and make sure the iac motor is working correctly.sounds like a vaccum leak though.

Thanks. I have checked for the vacuum leaks and have
not been able to find one but realize this may not be
trivial for me to find. What is the iac motor? If this is the air conditioning moror I have
had trouble with the air conditioning on this car since
the beginning and they just gave up trying to find the problem this year