I've always wanted a DS5, can't believe it's happening!

I believe it has NAC Wave 1 - the software had Carplay and Mirrorlink available, and FW 7.1.3.
I think it should have the Connected Services, but I'm not sure. It had the DS and SOS buttons on the roof.
I've seen the fantastic work put in by @MacSlavko to code the NAC units via Arduino and convert from the older RT6 to the NAC W2 - but I just want to clarify a few things when going a much simpler Wave 1 to Wave 2... I think points 1 and 3 are answered somewhere but the translation is a bit ambiguous, so want to double check.
1) Is it JUST a headunit replacement required (I think so)? No need to replace screen and cables etc? 9821908980 is the suggested part.
2) Is there any difference in the standard W2 units, and the HW2019/HW2020 units?
3) If I buy 2nd hand, do I need the original VIN number from the donor car still?
4) If I don't have the donor VIN, will the Connected Services ever work correctly?
I understand it's preferred to get a NAC W2 from a DS5, but given how few (if any) came with one that's almost an impossible task. I was planning to just load the normal W2 DS5 conf provided on github and double check the settings with my W1.
It does seem grabbing any other NAC W2 in the UK is fairly reasonable (a few at £130 available near me) - but if it needs the Donor VIN I need to be a bit more careful.