for example there's a quest where you mount a gryphon but i'm not sure how to display the abilities on the actual bar.

Whatever bar you consider your "main" bar needs to have the vehicle, possess, and override states checked in the bar configuration window

I actually got vehicle working now except now the icons for it are invisible.

That shouldn't be the case. Which version of Neuron are you on and are you sure you are up to date? On all of my toons vehicle buttons work exactly as they should