Paul,

I did a similar job years ago, and was in the same boat as you.. not knowing anything about pianos, I thought there was no way that it could have an audio out..

sure enough, underneath the piano was a little module doo-hickey.  It not only had audio out, but it stored songs so the piano could play by itself.

We popped a hole through the floor, routed the wires and piped it through the house using a Nuvo system.

Was easy, and kinda cool all at the same time.