All the orginal repaints y'all did for the old FS9 Seaking will still fit, just convert to *.dds and it should all still map ok, that was one of the over riding critierial with the rework, ie old textures must still fit.
Glazing, I honestly cant say, having flown it for months now it not something I noticed, I tend not to like the reflective type but do like a hint of something and as I haven't noticed either annoying me can only conclude there is a small hint of glazing there, but will need to check once I get home after night shift.
Gauges, I think they're 2D, but may have 3D bezels and modeling but a 2D placard and needles etc, cant say its ever bothered me, will need to check tomorrow or another tester may jump in first.
The original Marine One specific model has not been included so I'm afraid your going to have to put up with psuedo repaints of a military hack.
Best
Michael