That sounds fairly manageable to me. If you are uncomfortable in trying it, first take an extra long nail or long fine screwdriver to pierce through the Styro-foam until you hit something hard which would be the beam, then accommodate the hollow square beam by adding 2" to the drill bit. That would tell you how long of a drill bit you will need. I assume you would need to go through just one beam to get to the adjacent ceiling light for power. A 1/4" dia. drill should be big enough. If you decide to take the next step and drill, as best you can drill in the center of the foam thickness and drill horizontally, not at angle, and you will do fine. Once drilled, use a straight coat hanger to continue pushing through the foam on the other side of the beam to reach the area of the light fixture.
Keep in-mind that I have not actually done it myself. It's what I imagine is required.
