I used to have a similar setup with a pioneer 507XD and panasonic PTAE900 (I think that was the model).
The TV sat flush on the wall, with an electric 8' screen mounted in the ceiling void above (standard beam and plaster board construction), the screen was (well still is) bolted to the beam and the screen dropped down through a slot in the plaster board (has been filled in now by a friend who is a plasterer).
The main considerations I found where, making sure the gain of the screen was correct (based on how bright your room is), lighting control (try to ensure you darken the room to a decent level and think whether you be using in day time) and also where you position the centre speaker, I had tried various options from mounting the centre speaker on the ceiling in front of screen position, this means that my centre was slightly forward from the left and right. In the end I opted for custom install speakers in the ceiling with a motorised centre that popped down when it received a 12V signal from my AVR.
In terms of wiring, I would advise 1 or 2 HDMIs and maybe even an inline repeater (dependent on the length of the HDMI). A USB lead for firmware updates for the projector. A local power connection, 1 or maybe 2, 12V trigger leads, one to accept a signal from the AVR and one to send a signal to the screen to come down.
In terms of the screen coming down if you go the electric route, you could either have a 12V trigger as above, a manual power switch or an infra red receiver.
Then there are options for a fixed screen, which would replace the TV, some screens have excellent abilities to absorb the light from a projector and can be used in normal day time viewing condition, I think Clare Newsome has one and could advise better.
Hope this helps.