Hey @jsmid! Stepping in for Tess here.
This isn't currently possible in the Wizard component, but it's possible in the stepped container actually 
You can conditionally disable the previous and next buttons. In my example, I'm disabling the previous button for the first and second steps.
You can also even conditionally hide the button (you'd put the same code in the hidden field at the bottom of the right panel).
If you'd like to continue to use the Wizard component, I think Custom CSS might be your best bet there.
http://community.retool.com/t/how-to-use-custom-css-in-retool-apps/17300
Let me know if you have any questions at all!