I have the prodigy with the Ford specific connector that will plug directly from the controller into the factor plug under the dash, very simple install. You can also view a video on etrailer.com that is located on the regular Prodigy link that will show you how to install it, it's a simple plug an play.
Here is a link to the install:
Tekonsha Prodigy Brake Controller Installation - 2003 Ford F250 - etrailer.com
It will also show you how to do the set up you are talking about, it literally takes about 1-2 min of driving to set it up once you have it installed and the trailer is hooked up, you just adjust the max voltage that is putss out to the trailer by adjusting the manual voltage knob on the controller to about 6 at first(12 is the max), run the truck and trailer at about 25 mph, and activate the manual lever on the controller and if the brakes lock up the max voltage is set to high, so bump it down a little and repeat. You want to get the max voltage to the trailer but just before the point where you lock up the trailer brakes. If when you tried the 25mph test and the trailer brakes didn't lock up, then bump up the voltage a little and retest until you get them to lock, then bump it down just until they do not lock. The prodigy and the P3 also have boost controls on them (3 levels, level 3 the highest), boost is the initial amount of voltage sent to the trailer when you first hit the brakes, with a real heavy load a higher boost level can help to slow the trailer and truck on the initial hit of the brake pedal, the manual will have recommended boost level for certain measured load weights, but you can play with this on your own and see what's best for the particular load you are carrying. Long story short don't pay anyone to do this, if you can used a screw driver(to mount the controller) and follow the manual to set it up, which is the same as I mentioned above than you should have no problem.
Now with all that being said my gooseneck never locks it's brake at the max setting of 12v, this is because my brakes are probably a little weak, just keep this in mind when setting up the controller.
The P3 is more or less the same as the Regular prodigy just has a nicer LCD screen and it can do electric over hydraulic brakes so it's really you preference, if you can find a good deal on the P3 I'd go for it, but the Prodigy works excellent too.