I think your Ford guy is full of shit.
As RonD is fond of saying "4x4 starts at the frame", and he is correct. To do this you need to remove the steering box reinforcement, and the engine cross member, both of which are welded in, and then replace said cross member with one correct to a 4x4.
Then you need to get the TTB front axle for a 4x4 and install it.
As for easily converting the AWD case to a part time, well that is not "easy". I'm not ever sure it is possible. There isn't a shifter provision in the case for one. The internals are quite a bit different. There is still a planetary gear set, but instead of a shift collar that engages and disengages the front output there is a fluid coupler, kind of like a torque converter, that is permanently engaged. So the case could probably be drilled for a shifter of some sort, probably E-shift, because the casting points are there. Turning the internals into part time is going to require a full tear down and transplant the guts of a part timer, which at that point you already have a part time case. So, maybe not difficult, but definitely pointless.