OK, thanks! Being that I'm a noob when it comes to all this, it took me a while to sort out the natural order of things. However, right after I posted my previous message here (not on vwvortex), I got the following from DV52 on vwvortex (as a response to another user's contention that OBD11 won't help), and he seems to confirm what I understood from you (however, he doesn't seem aware that the amp needs to have its CP removed as well):
"Need to separate in your mind the concept of SWAP (i.e. SoftWare As Product) and long-coding/adaptation channels changes:
SWAP generally affects the module's firmware and it is ALWAYS requires an activation code that is specific to your VIN - so, can't be transferred to other vehicles.
Long-coding/adaptation channel changes are the stuff of diagnostic cables like VCDS/OBD11/VCP. These are not considered to be based in the module firmware - they generally reside in non-volatile "operational" memory within the module.
As a general rule, my observation has been that VCDS and OBD11 (and VCP) have roughly the same capabilities - albeit there are many differences between diagnostic cable in the way that they operate and especially in the way that the data is presented to the user.
As to your question about adding your new components, the first thing to recognize is that what I think you call the "head-unit" ( VW call this J794) will be at odds with the CAN Gateway's understanding of the identity of this module at the previous ignition switch-on. This checking process by the CAN Gateway module happens every time that you switch-on the ignition. It's intended to combat the black market trade in stolen equipment and it's called Component Protection (CP)
So- unless your new Head-unit has been hacked, you will need to remove CP error as the first task after fitment. Officially, CP removal requires connection to VW's FAZIT database and only registered VW agents can do this.
Yes, and then you will need to tell the CAN network in your car to start managing the external amp - this is done by registering the "sound system" in the CAN installation list - it's at address hex47.
The next thing that you will need to do (programming wise) is to tell the Head unit to by-pass the normal speaker plugs at the rear of the head-unit and instead to wield the audio data to the external amp via the optical cable that you installed between the HU and the new amp. This is done by enabling the MOST facility in the long-coding software-switch @ Byte19, Bit5. And you will also need to change Byte 4 to hex00 (it will be hexFF as factory set), and change Byte11 to hex02 (it will be hex01 as factory set)"