My buddy and I got the Glock 19x about the same time, but I opted out of the factory night sights to save a few bucks while he got them. Anyway, fast forward a few months and he decided to mount a red dot on his and said he wouldn't need his GNS anymore and offered them to me.
Along with lending me his slide, he also lent me his NcStar Universal Pistol rear sight tool.
The thing was very easy to use and very intuitive, but youtube vids helped. I was easily able to slide his GNS off and slide them onto my slide. I threw my plastic ones onto his upper with little difficulty.
Next the front sights.
I'm guessing he ordered this hex-key socket separately
Easy enough to get off.
The sight tool even accommodates slides with RDS mounted.
The swap took no more than 10 minutes.