Gasoline is listed as "flammable" and diesel is listed as only "combustible". There is no application for an auxiliary gas tank, (like in the bed) for a gas anything. You can add a bigger integrated tank though. Been there and done all that.
There is some advantage, but not much, to just new door speakers. Check around and see what you like. Without a new amp and other components, it'll just be a start.
I don't know why, but congratulations on buying a hybrid truck! I'm sure that's the future for cars in America.
http://media.gmc.com/media/us/en/gmc/news.detail.html/content/Pages/news/us/en/2016/feb/0225-sierra-eAssist.html
I had a 2015 F150 Lariat until a month ago. I am surprised to see that I am the first one to say that I really liked the floor shifter. It was a very comfortable place to rest my hand while underway. Intelligent entry and keyless ignition were great, for me, too.
The F150 had plenty of console storage for me, and I'm a contractor who drives from jobsite to jobsite all day.
The shifting is really electronic now, even though the shifter feels connected. Since in flat-tow mode the park position is disabled, it may be related to that. It's a dealer issue no matter what .