I originally had Best Buy install an Alpine in my old '99 Eclipse. Then, I re-installed an 8454. I couldn't use the Alpine harness, so I just matched up all the wires, spliced the, and taped them together. I had the single DIN unit from the Best Buy install, so I just kind of rested the 8454 on top of that, it was a tight squeeze so the head unit didn't move around too much.
The bezel around the head unit and A/C controls was pushing up against the head unit, so when the face would open it would cause the bezel on the head unit to pop off. So I took a Dremel to the Bezel on the car and made some room.
Not really a hard install, probably wanna get a harness, though and possible be prepared to cut.