Visited Chevrolet dealership yesterday. Interior lights issue resolved as a training issue. There is a little button on the dash which toggles the automatic lights on and off. They also gave me a printout of the latest technical bulletin on P0017 issues, and shortly after my visit the P0017 check engine code cleared itself and hasn't come back on since.
IMHO the problem with my truck may be that it sits sometimes for several days between uses and the 5W30 oil in seeps down from the hydraulic lines that control the cam timing while it is in the garage. When I start it up cold, sometimes before it gets pressure back up it trips the code. The on-board computer, according to Chevrolet service will clear the code if on three consecutive starts the problem is not sensed. This may well explain my "intermittent" issue with the Check Engine light.. I guess I've got to run my truck a bit more.
BTW winter mileage for the last couple of hundred miles has been 17.5. My Ford Ranger which was a 1995 was getting 18 on similar use with its' 2.3 Liter Mitsubishi, but it didn't have nearly the power of the 2.9 Liter Chevrolet 4 in my new truck.