I am going to put in the d3 in my 03 expedition this weekend and I have read some threads on here about the steering wheel controls not working with aftermarket radios. Is this true, do i need to put some device in there to allow those controls to keep working? If so, why would they not continue to work?

Thanks in advance!

You need a PAC SWI-PS.

Then they will work. There are too many different steering wheel control "standards" that Pioneer didn't want to cover them all, so they chose a single standard and the PAC SWI-PS can translate between factory steering wheel control signals and Pioneer signals.

How are those wired in and are they hard to do?

Nah, pretty easy. Generally just 3 wires and one plug. The 3-wires are +12V switched, Ground, and steering wheel remote wire. All of these are are available at the stereo connector. The plug is a 1/8" (headphone style) that plugs into the back of the Pioneer.

Then you just program the SWI-PS unit to tell it what kind of vehicle you have. It only has one button for programming, so it's fairly simple to do and you only have to do it once. It stores the programming in an EEPROM so it keeps its settings even if the battery should go dead.

I looked and they are compatible with 03 Expedition, so a SWI-PS is exactly what you need.