"If the universe is constantly expanding, will the stars at night get dimmer and further between?"

As the space-time continuum stretches, taking the galaxies further and further away from each other, the distant galaxies will appear dimmer as viewed from earth, but not anytime soon (from a human perspective of time). Think of it this way: we're here at the best possible time in cosmological history, both for life to flourish, as well as to observe the rest of the universe!