Help With Eonon GA5166F Install w/Factory NAV no DSP

[we350z]

Hello - I have a 2000 BMW X5 (e53) w/Factory NAV and no DSP.

I recently purchased a Eonon GA5166F on eBay for about $350 as my 16:9 Boardmonitor LCD screen is starting to crap out and not meeting technology expectations otherwise. I read some reviews here and thought the Eonon units were pretty much plug and play as long as you don't have DSP.

Apparently this is NOT the case with Factory NAV and is only really plug and play with the "business" radio that has the 40 pin connector behind the dash.

Neither of the supplied harnesses appear to fit the two twelve (12) pin connectors behind the dash (one blue, one white) I removed from the rear of my Boardmonitor.

As I understand from researching on this and other sites the radio module is actually the same for most BMW models of this era (including E46, etc...). I have seen this stuff under the spare tire below the trunk area.

I have sent a support request to Eonon but I think I pretty much only have two options here:

1) Purchase the 5 meter (16.5 foot) A0573 17 pin + 40 pin Extended Installation Wiring Harness and run it from behind the dash to the BM54 radio module under the trunk area as described here.

2) Since the Metra 71-9003 harness cannot be connected to any speaker line level inputs from the X18801 (blue 12 pin connector behind dash) it can only be connected to +12V and ground. I can then connect the RCA preamps from the Eonon to my GromAudio AUX input for which I already have a long cable run up through the center console.

It would be necessary to keep the Boardmonitor because if the vehicle battery is disconnected input will default to FM and will require old radio be plugged in to switch it back to AUX). Was thinking for this I could make a simple short cable that would tap the remaining pins to the relocated Boardmonitor original harness and just connect 12V/G from elsewhere. I found this idea here.

Only other question is if anyone has used factory NAV antenna with any success by running an extension coax to the rear.