Pop port adaptors can be ok for a short term solution, we would need a better decription of your cradle to tell what kit you have now, my advice would be to buy a new CK-7W, you can never tell weather your existing car kit will work or not until you have tried it. You will save money in the long run.
Danny b
Nokia Accredited Installer
If my answers help you, give me a Kudos. Its like a pat on the back.