I have a Hampton Bay ceiling fan with a night light feature encased in a mission-style top glass. Anyone know how to replace the bulb w/o taking the whole fan down?

There's usually a way to access it from the bottom. What model do you have?

I wish I knew; but we bought the house from our kids who never save the paperwork from anything. Ugh.
It is a five paddle mahogany fan w/ 3 mission style lights and a large mission style top light (cream and green glass w/ black stained glass like markings). I know the large top light lit because we used the night light feature a few times before it burned out. Any other ideas?

Not without seeing it. Perhaps if you snap a picture.

But honestly you should be able to figure it out if you look hard enough. Either the glass unscrews, or there's a hatch to enter the inside, or it's from the top.