I thought the stairs would be the hard part, but the railing turned out to be the hardest part. All the parts came from Lowes. I sanded and applied polyurethane to the wood parts. I tried the water based polyurethane, but I wasn't happy with the results, I'll be sticking to the oil based versions of Minwax next time.
The directions (see hyperlink above) are like a choose your own adventure. The problem is on top of bouncing back and forth, the nomenclature is confusing and difficult.
In my particular case, the original railing that goes the rest of the way up the stairs is NOT parallel to the kneewall (the part the lower railing is resting on). The only piece that didn't have to be cut with an angle was the first starting newel (post at ground level). That means that the bottom shoerail (piece that holds the bottom of the white posts) is at a different angle than the railing. Which means the newel posts at either end are different sizes and we had to be careful cutting the white posts to make sure they fit.
This literally took my father-in-law and myself all day for a 4 foot section of railing -containing 10 pieces of wood. I'm happy with the way it came out. The old railing was a hideous steel POS.