2 truck buying questions

First is the trans, I currently drive a 10sp. I'm looking at trucks now and a few pretty nice ones are 13sp. I know HOW to shift a 13sp, just never actually done it. I'm sure like anything once you adapt to it you no longer consciously think about it anymore and I've read that they get slightly better MPG, do you guys feel a 13 is worth it?

Second is new truck checks. I'm not rushing into a truck blind and thanks to this place I'd want an Oil analysis done on a potential truck. If they recently changed the oil, would that tweak the results? Also thanks to my current job I've seen how insanely night and day a truck can be with/without a load on it. My company has some Volvo's that bobtailing will burn the tires of of themselves, hook up to even 20k and your doing 45 on the highway with those speed demons! So I'm probably going to want a dyno done as well. Do dealers get pissed if you want to dyno or oil check a potential truck?