Not according to a friend of mine. However I haven't heard one so I
reserve judgement. I'd visit a Halfrauds store and ask for a demo
before I bought one.

Not if you buy a griffin ( ipod style...)
HOWEVER

the metal coated windos of a 406 will prevent it from working as it
should.

but there is a solution for that, you can put a transmitter in line
with the antenna cable ( do a google on that)

the other thing to look for if you happen to have an ipod is an
Icelink from dension,  the head unit of a pug is clarion afiak

http://www.dension.com/icelinkplus.php

Then, there is a line input on the CD changer input  though it might
be a bit picky if you want to connect a mp3 player on that.
I solved it by leaving the cd changer in place, parralel the MP3
players output on the cd changer and putting the cdplayer on pause..
all functions of the head unit keep working as does the cd player.
but that was on a blaupunkt
the inputs are easy enough to find, and usually red and
grey/white/black and a common ground between them

if differently coded you can find them by using a 1.5 volt batery
solder some leads on it, turn your unit on( max inout on line level is
as much as 7.8 volt) find the common groud ( NOT THE CAR CHASSIS)
and poke around till you hear the left and right speakers plop a bit
of course you dont have your head unit at max volume when doing such

good luck

marc