Hi, I need your help

I just bought an NAV-MP3-DIVX-BLUETOOTH-IPHONE sytem AVIC F500BT and want to install it in my XJ8 3.2 Sovereign 1999.
http://www.pioneer.eu/eur/products/1...0BT/index.html
It comes with an additionnal amplifier 4x50W.

I decided to choose this option to keep the existing Stereo system, steering wheel controls and cd charger. I bought an on dash mount PROCLIP 852515, I have to install the system. But I still have some questionmarks:

1) I dont know if my stereo has an external amplifier. If any where should it be ?
2) I don't know the brand. Is it important ?
3) I will keep the existing stereo, so I need 2 harnesses, one with a female-plug-toDIN another with a male-plug-todin. right ?
4) there was a factory phone that I unmounted. I think I cannot use the plug available in the console. am I right ?
5) If I don't find the right harnesses, I envisage to cramp my wires directly on the 8 speaker wires going to the stereo in addition to the mute plug. Am I right ?

this is what I found somehere...
2000 Jaguar XJ8 Car Audio Wire Diagram
Car Radio Battery Constant 12v+ Wire: Green/Black
Car Radio Accessory Switched 12v+ Wire: Black/Pink
Car Radio Ground Wire: Black/Green
Car Radio Illumination Wire: N/A
Car Stereo Dimmer Wire: N/A
Car Stereo Antenna Trigger Wire: N/A
Car Stereo Amp Trigger Wire: N/A
Car Stereo Amplifier Location: Behind the Glove Box
Car Audio Front Speakers Size: N/A
Car Audio Front Speakers Location: N/A
Left Front Speaker Positive Wire (+): Orange/Green
Left Front Speaker Negative Wire (-): Blue/White
Right Front Speaker Positive Wire (+): Tan/Green
Right Front Speaker Negative Wire (-): Green/Orange
Car Audio Rear Speakers Size: N/A
Car Audio Rear Speakers Location: N/A
Left Rear Speaker Positive Wire (+): Gray/Blue
Left Rear Speaker Negative Wire (-): Brown/Yellow
Right Rear Speaker Positive Wire (+): Black/Violet
Right Rear Speaker Negative Wire (-): Orange/Violet


could you help me sort this out and I'll post photos of the installation steps