Considering upgrading my wife's Moto G5 to a Moto G7 as the current one has had a hard life and is starting to fail. The Moto G7 on Amazon doesn't list 4G band 28, but does list band 3 and 7 (Vodafone frequencies here).

Not sure if it has 4G band 28. This site and this site both say it does, and both the cheaper Play and Plus editions include it, and the G7 sold in NZ has it. I have seen that there are versions without band 28 though, so I would probably avoid it. The play / plus editions both have band 28, so not really a problem.

How important is band 28? My best guess is band 28 is has longer range, which might be more important if you're say driving between cities or in low coverage areas? We live in Wellington inner suburbs and work in Wellington city, so I doubt coverage will be an issue except maybe on holiday - and we can hotspot off my phone if we need to.

Looking to buy from the USA as it's NZ$300 plus shipping, in NZ it's $500. In NZ you get a 12 month warranty, from the USA no warranty, though I would hope that if it's DOA Amazon would replace it.