There is a gems and a mems, as long as you replace gems for gems etc you will be alright, there are differences with gems and mems. I you replace a gems with a mems engine you will need some of the parts, cam sprocket etc from the old engine as the set up is different.
As long as you swap a gems for a gems, just take off any bits that are on the old engine, sensors etc ( Cam and Crank ) that are not on the new one and bang it in....