I just got the new RailKing proto3 Lackawanna TM and ran it for the first time today. Everything DCSwise appears to be the same as with proto2 except possibly the battery status under the "Advanced" menu. Since it has no battery, you always get a "low battery' reading.
I guess you no longer get a regular locomotive specific manual. The only thing included was a generic Quick Start Manual but there is a reference to "the complete manual" available at the MTH website. Has anybody ever found such a manual? Here is the product page and as you can see the manual and nearly all other links are grayed out.
http://www.mthtrains.com/content/30-20096-1
BTW, the locomotive looks great, runs just fine, and is a real bargain in today's market.
Ken