There are 2 plugs in the back of my stock head unit. One larger one (which the adapter from our 2006 Explorer clicks right into, but a couple of the wires are different) and one smaller one. I'm not sure which wired are for the factory sub (mine has no sub anyways) but those are the only wire connections at the back other than the antenna. I'm not sure on a truck with no sub if any of those wires contained in those 2 plugs are just unused and would go to the sub if the truck had one, but there are a few empty slots in each one...so maybe the wires aren't there, but would be in those slots.
My truck does not have heated seats. My plan, going back to my last post above, was to tap off of the heated second row seat fuse in the passenger's footwell fuse box. I haven't tested the circut, but I assume ot only has power when the ignition is on. This would complete my install, along with the steering wheel control converter.....
BUT........
My wife has decided she wants to keep the SYNC, mainly for the bluetooth but also for some of the other voice commands she's gotten used to using. I KNEW that was going to happen lol. So I ordered the PAC kit that maintains the SYNC functions and plays the SYNC audio voice through the aftermarket head unit's aux input. We'll see how that goes.
It's actually very easy. The panel around the head unit has 4 main clips. I started gently prying at the bottom of it below the 12v power outlet. If you take your time and work your fingertips around the outside it will pop off. If any of the 4 metal clips stay in the dashboard make sure you pop them out and place them back on the tabs on the back side of the panel before you put the panel back in place. Once the panel is off there is enough slack in the HVAC controls wiring to move the panel aside, and then it's just the typical Ford 4 9/32 screws holding the head unit in.