How do I replace Blaupunkt cassette player with CD player?

Hi all. I've removed the standard radio cassette and found the back of the original radio plugs straight into the back of the radio 'holder'. The problem is my replacent CD has the same plugs but they are on the end of two sets of wires coming from a much smaller plug on the back of the replacement CD/radio and when I plug them into the back of the 'holder' they protrude to far to slide the new player all the way in.
I've tried to remove the sockets at the back to see if they were some form of adapter but no luck. Should they come out? Any suggestions gratefully received.
Cheers
Rob