You've been to AprilAire.com. Why don't you 'ask' them for an e-mail or FAX copy of the Installation Instructions. I'm sure they'll send them to you. Or, you can stop by places like Home Depot or Lowes and see if that unit is sold there, and see if an opened box has what you want. (Because you're a nice guy, have the store make a copy for you. Don't just 'steal' them ...)
This is the only help I can give you. I do know that the unit can be wired to turn on when the Blower is started. My best to ya and hope this helps.