My advice - post this on the Classic Trains forums. You'll get a larger and more experienced O-gauge crowd over there.
Just FYI, I've installed an in-track Kadee uncoupler for HO recently. The instructions say it works better with DC, and that seems to be the case. Also, this thing really gobbles up the amps when you turn it on, so it's best to have an independent power source for it. (I found a 12-volt DC wall-wart in my surplus pile. Perfect.)
My track was already installed, so I did the job by cutting through the ties and slicing through 2 inches plus of roadbed and foam, and then installing the unit from below. Believe me, that's the wrong way to go about it. Install it in the track as you're putting it down, not later.
It takes an iron man to play with a toy iron horse.