How hard to replace headlight switch on 67 Valiant?

Only 1 screw holds the fuse box in place. Remove it, move the fusebox up 1/2 inch and toward firewall 1/2 inch to clear the bracket. You'll have ample space for finger on switch stem release button.
And just FYI we don't push the button to reinstall this stem. To do that could wreck the latch. The tapered tip of the stem guides it into a spring loaded "keyhole" styled latch.