I had mine profesionally installed - do you want to use an external speaker or connect it to the front speaker?
The guy who installed mine used a box which contains a relay to do the speaker switching - I think the only non-standard thing then (the parrot plugs into it via a standard ISO connector) is the mute - also I remember he had to jumper over the subwoofer connection because the lead didn't connect that across..
However, if you haven't already bought a Parrot handsfree kit, I would recommend you don't. I personally think it's <insert favourite expletive> and would not recommend it.
I used to have a hard-wired Nokia (HF-1 I think) kit in a Renault Laguna (installed it myself) - I could drive on a main road and many people had no idea I was in a car. With the Parrot in a GS300 (much quieter car), most people find it hard to hold a conversation and complain of hearing their voice echoed back to them and a huge amount of road / wind noise.
Also, with my handset (a Motorola V3, with varying firmware versions) - it repeatedly drops calls, or I will hear the caller but they can't hear me, or worse it drops half of the calls and leaves the caller connected but won't allow the call to be terminated from the control panel. Customer support was not very good.
It's cheap and it shows, unfortunately.
Just my thoughts..