When I go over a bump or a dip (causing the front suspension to flex), I get a really dry sounding creak in my front suspension. I've lubed the ball joints with PJ-1 chain lube, but that only seems to last for a couple of days. Should I take it into a shop and get it professionally lubed, or replace the ball joint assemblies altogether?

 

Its most likely the bushings in your upper a arms. Just buy yourself a new set of them and problem will be solved. Comes with those bushings as well as a new ball joint.