@Lokgolo
Since I don't have Fender audio, do I gain anything from upgrading the amp? (I understand it's not necessary, but want to know since I'm making QOL upgrades)
With no Fender your car doesn't have an external amp. Speakers are being driven by the MIB internal amp... so nothing to worry about on that front.
I read inconsistently that I need to upgrade the gateway module. Is this correct?
For MIB upgrade no gateway upgrade needed.
Does the revision of the screen matter? Or for the MIB? (No suffix vs. A. vs. B, etc.? Hardware revision?)
The revision will determine which buttons it has. I don't off hand know which is which but eBay works to see. One of the letters has mute button, one letter has band instead of radio, etc. Any screen will work though
I assume I can reuse my existing trim for the screen since I'm going 8" matte?
If you're going 8" matte you need new trim. If you're going 6.5" matte you'll keep your existing trim. The 6.5" fits, just has smaller bezels.
What is the cost of having Jack or simaservis1108 perform the CP removal and coding? (I saw simaservis is inactive now, I'm open to other reputable leads if Jack is unavailable, too)
I'm not sure honestly. It's been literal years since they took care of me. I believe simaservis can be reached on telegram but scheduling can be tough. I've used VAG Retrofit & Coding for a lot of work though, also available on telegram.
Just in case you don't know, the USB port doesn't come with harness. Most source that harness from Ali but can probably find one shipping from within the US on eBay, with a little markup, haha. EZT also sells the harness for about $50. If you go that route get the harness from them and source the USB port wherever you want (they charge something like $75 for it).
Also not sure what nav cable you're referring to. Your car, like mine, will already have GPS antenna and cable/plug at the MIB. Seems the early MK7s mostly came that way. Later on they started with different (less equipped) antennas.