Hi All,
ccfj1 has been helping me via email with this install for the past few weeks.
i just wanted to post up here to see if there are any thoughts on where i need to go next with this.
i will try to outline, as best i can, as to my current setup, what equipment i have ordered and what suggestions have been made to me.
i am hoping to complete the install DIY as much as possible and only rely on professional help if i really need to. if it gets to the point where i need the help of a pro i want to be able to specify to them, exactly what i need done so a clear roadmap of actions, along with having the right parts to hand is vital.

i want to thank ccfj1 for his help to date, and i want to thank, in advance, anyone who has something to add to this thread

to start, my current setup.
a 2002 E39 M5
TV installed at factory
16:9 screen installed at factory
sat nav NOT installed at factory.

my understanding from reading various manuals, and talking with ccfj1 is that this means i have the onboard monitor loom installed, but not the supplementary harness for sat nav (cant find a part number for this)

i have purchased the following items
Mk4 & mounting bracket
new trunk trim panel
gps antenna (no extension lead)
and a retrofit loom as recommeneded by ccfj1

the situation i am now in is that, as i dont have any nav cabling in my car i have 2 unconneceted blocks on the loom and, as i have no gps antenna preinstalled and no extension cable, i have no satellite signal.

what i am trying to confirm, from this point on is -
what connections are needed on the retrofit loom (there is a black 6 pin with 3 wires connected and a black 12 pin with about 8 wires connected)
where can i put the nav antenna to get a signal
do i need to purchase anything else
will i need to tap any wires

my aim is to do as much as possible in the trunk as, since there is no need to install the 16:9 monitor or loom, i want to avoid taking apart the interior if possible.

the installation instructions i have been trying to follow are here
i can post pictures of any part of the car towards the end of the week as its in getting a bumper repair for the next few days and i can post pictures of any of the wires or parts if that will help

so, there it is (i hope) sorry for the long post, i hope as much of it as possible is accurate and hopefully you can help me get over the last few hurdles