Yeah Jimmarla I read your other post about the PPE tuner and it's like a Bullydog or Superchips in that it just plugs into your Diagnostic port and re-flashes the computer based on the power setting you want to give it. It stores your stock programming though so that you can return to it if you need. I'm not 100% sure if it has any on-the-fly settings (other than transmission reset/re-learn..?) but they come in 3 types. Economy, towing, and hot each with a different price tag. It doesn't have any gauges but it can read and delete codes if the truck throws them with the tuning added.
I also have the Edge and really like that it has a gauge package and an EGT sensor in with the kit. I installed the sensor in the manifold and I mostly have the PDA show me: Boost (PSI), Trans. temp, Engine temp or intake air temperature, and EGT. It has up to 4 that it can show at once and CAN show things like. IAT, EGT, Eng. Temp, Fuel Temp, Trans. Temp, Backdown %, Load %, Gear (with lockup showing), Throttle %, Barometric pressure, etc to name a few. The other thing that is nice about the Edge is that it's all on-the-fly and you can go from Stock to: tow, drive, race, extreme, hot in a matter of seconds as you are driving. It can also read and reset codes.
If the PPE isn't stackable with the Edge (duration may be doubled...) I would possibly consider trying a PPE instead of the Edge. It's very nice to have that set of gauges though and it gives me a pretty good idea of what's going on with the truck. Can just get a boost gauge and an EGT gauge and have those on the A-pillar with a 2 pod mount...or 3 pod mount and grab trans. temp if you want. Or any 3 for that matter.
Yes you can remove the PPE without the dealer knowing. You re-flash the computer to stock before you take it in is all.
I had noticed a fuel economy improvement using the Edge, can't say about the PPE though but they have a great reputation as far as I know for the Duramax.
Something to consider Jim.
Edge w/ Attitude = $950.00
PPE economy = $520.00
PPE Tuner = $620.00
PPE (225+ HP) Hot = $920.00
3 Gauge pod (new) = $80.00
EGT sensor = $190.00
'Other sensor' = ~ 150.00
So you can basically get either of the first 2 PPE tuners and a gauge package for less (or just as much) than you can buy an Edge! 2 mpg on average more is still 58 miles haha

. Hopefully it gives closer to 4 and you can get another 96 miles in there.
58 miles more = every 6th fill up is free lol!
96 miles more = every ~ 4th is free.
Fuel savings = roughly 16 - 25%. You "could" pay for the tuner(s) (without the gauges) in JUST 26 - 43 fill-ups! Promising information isn't it? It might be wrong with some of the conversions I had to do, I used your mileage at 14.5 mpg (empty) to get this info.
I have not yet tried the integrated trailer brake controller. My tires stock were 265's and I'm in a 2500HD. You don't have to get a dually for a 3500, I haven't checked the stock tire size on them. I believe all 3500HD's are long boxes though, if you 'configure' your GMC that's the only option you get, however you can get a single cab, ext. cab or crew cab configuration.
Lunch is over, I wrote too much anyway.