I got the headunit a little over a year ago for $300. It's pretty much the cheapest way into in-dash nav. It also has bluetooth which is really nice. You can see the mic in front of my speedometer in one of the pictures. I'm sure there's a way to keep the DVD functional, but it may not be something you want to get into. I recently install the steering wheel control interface so I could finally use my steering wheel controls again.
The LEDs are the easiest. They're sold at AutoZone and Advanced Auto Parts in 24 to 36 inch strips that just adhere to the bottom of the headlight or wherever. The light that I didn't photograph has about 5 or 6 dim LEDs for some reason. Not sure why, but I'll look into it once it warms up. For all my other LEDs (parking lights, turn signals, puddle lamps, done/reading/cargo lights, footwell lights, mirror turn signals, and license plate lights) I ordered them from superbrightleds.com. Excellent website as they have every type of LED you can imagine. I've purchased $90 worth of LEDs from them, but it would be less for you because Explorers don't have footwell lights, mirror turn signals, and I believe Explorers have one turn signal/parking light bulb per light, while Aviators have two per light.
I'm on the college budget too so I haven't done too much lately. The Aviator won't get a wash until late February when I'm home next, but I have some pictures from the last time I detailed it that I'll throw up and link soon.
if i plug in some dubstep and turn it up it gives me a headache haha.
