You just beat me to it matehttp://www.civinfo.com/forum/how/41667-how-install-xcarlink-2008-civic-ex.html
Here's a how to, don't know about the CD changer question though.
brilliant! cheers mate, will give them a emailHi Nollit
Please look at this link from UK official XCarLink website
As it stated there at the bottom, you can use Y cable to retain your existing CD changer
Honda Y cable*::*ACCESSORIES*::*XCarLink
If you want to be sure for 100 percent, just send them a question, but i think it will work
By the way, I also installed XCarLink and it rocks!