Radio Question CD-23

Hi, I have a '03 Boxster S with a CD23 radio and was looking to add an auxiliary out jack to it. I had emailed Becker about this and evidently, I would have to mail my radio in to them in order to get the upgrade unlike the CD-220's. I was wondering if anybody else has had this done to their radio in the past and if it worked well. Specifically, I was concerned b/c it seems like the fix will take over the FM receiver so whenever something is plugged into the auxiliary port, it will automatically convert to aux in. Was curious to see if the other radio options like AM or CD would still work. Also, would my car alarm be set off if I take out my radio out and drive around for a few days or would I have to pull out some jumpers. Additionally, would my car be backward compatible for a CD-220 radio? Basically, I'm looking for a way to keep my car and stock appearing as possible.

Andrew