This is something a beginner can repair. This is normal stuff for those who ride bikes and don't go to a shop for little repairs. Replacing a tube (and fixing it with a small vulcanizing kit) is biking 101, and there they're not even expecting you to repair that. Just check how to replace the tube of a wheel in a youtube video and while at it, check if your strip needs alignment. Tyres often go flat but you normally feel that something is off because it feels "smeary".
The warning is just for those who are not the slightest bit technically inclined and don't feel like doing any of this. To avoid lawsuits.
I bet in the Netherlands any 10 year old kid could check if your wagon is affected and if it is, align the strip.