In order to create the diegetic text (diegetic means that it belongs in the “real” game/media world, not a representation that only the player/spectator can see - like a HUD) you should use a Text Render actor (or component):
With this in the scene, you can easily change the text by using the Set Text node (in this case, the text changes when you enter the trigger):
I hope that guides you on new directions.
I`m happy to hear that you are having a blast with Unreal. It only gets better. 