Try the 737-800 package by Arjan Scheffel (as738.zip, here http://www.wspilots.com/index.php?page=4&action=file&file_id=2170). It's a large download at 52mB, but it's the most complete freeware 737NG panel I've yet come across, and in some respects better than even the PMDG panel because of the incorporated sounds. It has an optional automated checklist with pilot and co-pilot voices so that you get everything turned on in sequence, plus environmental noises like other jets taking off when you are on the ground, cockpit and cabin voices, V-speed callouts and more. I have it aliased to all my NGs.

Yep, possible - might even be as easy as putting the control gauge line (this one, I think - gauge00=AS738!Functions,0,0) into the appropriate panel.cfg line - try it and see what happens. As long as the author hasn't done something as devious as making the individual gauges dependent on each other, it may work! If not then you'd have to study the gauge XML and figure out which pieces to use in order to work the sounds. Gets more complicated then. Otherwise, it's down to some cute XML programming-from-scratch to get the sounds to play at the right conditions.