As I understand it, the earlier Galaxies up until around (mid?) 2004 build date would have had the D5W-Z heater fitted. Around that time, a small 'refresh' happened and a few cosmetic changes were applied such as the modified 'Lexus style'

rear lamp clusters, chrome trims on the front grilles and foglamps, revised wind deflector at the top of the bonnet/ bottom of the windscreen, new trim/ fabric patterns on the upholstery and revised alloy wheels designs etc. I suspect that the 'refreshed' models would have also had the newer D5Z-F heater fitted as part of the change in production. Presumably Alhambras and Sharans also had a similar refresh at the same time, but I don't know that for sure. The problem is that the changes would have been implemented after a certain build date, so you can't be sure purely from the reg no. as some cars could have been sat around for a while prior to being sold- you might find some 'refreshed' models on reg's as early as '53 plate, but also some of the earlier models running on '04 or even '54 plates, depending on how long they sat around before being registered.
So I'm surmising for the Galaxy, if it's the 'refreshed' model, it'll have a D5Z-F. If it's an earlier model, it'll have a D5W-Z. As for part numbering, a 7M3 xxx xxx reference is VW's part number for it, the 25.22xxxx format part number is likely Eberspacher's own reference for it.
F.W.I.W, 7M3 963 319 would seem to be the correct part number for the glow plug on a
2005 Sharan with D5Z-F fitted (number 16), I can't help with the Eberspacher part number though because Eberspacher themselves don't 'officially' support the automotive fitment heaters such as the D5Z-F (even though it's virtually identical to models that they
do support), they simply direct you to your car dealer spares department!