This is definitely the nav system made for the 4Runner, and not the Toyota nav system made for the Camry/Solara? Both will fit into the 4Runner. The Camry system can be had for that price, but lacks some features included with the 4Runner model (which is close to 4K list, not including gps antenna, mic, & steering wheel buttons.)
From what I understand, here is the breakdown of features for the different units. If I'm wrong somebody correct me.
4Runner nav:
3CD changer, reads MP3 CD's, bluetooth capable, aux input capable, XM & Sirius capable, voice commands, buttons light up orange (same color as dash).
Toyota Camry/Solara nav:
Voice commands, no MP3 CD's, no bluetooth, no aux input?, lights up green, XM & Sirius capable.
Eclipse 5500:
No voice commands, no bluetooth, reads MP3 CD's, aux audio & video input, plays DVD movies, lights up green, parking brake wire can be grounded to allow navigation entry and DVD playback while driving, has rear camera input which can be used while driving, Sirius capable, HD radio capable, ipod ready with Eclipse adapter, 5V preamp output.
With the exception of three wires (speed, reverse, & parking), all of the above units should fit into the factory wiring harnesses, and can be controlled with the steering wheel buttons. You may also need a trim piece to fill around the edges properly.