Help converting RGB Images to CMYK?

I am working with a CMYK Freehand design, and it includes a cut out image on top layer. The image is in RGB. When I export it, I am getting a colour shift on the transparent areas.

Should I be working with a CMYK cut out image? If so, how do I convert my RGB image to CMYK, keeping the transparent areas of the cut out?

Help much appreciated (ASAP)
Regards

Geoff