Under no circumstances would I put the screen on the door wall.
Your screen size with a 10-15' viewing distance would typically be between 100" and 140" diagonal. 92" is nice, but not very large, which is a very poor decision IMO - especially if you want to create a cinematic experience.
You don't have any room for speakers with a screen in the corner like that. It throws everything off.
Turn it around, and the screen can be on center, speakers can be properly placed left/right/center of screen.
If you are not self installing, then I assume you won't be building a screen yourself. There are great prices online for 'cheap', but decent enough screens, such as these...
Widescreen=9&f-Fixed Frame Screen=40&show=40&page=1&f-Black Velvet=105
$300 to $400 for a pre-fab screen which is pretty easy to build/hang yourself.
I think all of this comes down to your budget at some level. Obviously you want to paint - walls and ceiling must be painted dark. Don't forget the ceiling! You may want to add some sort of rug at some point to cover the light color for best results. And unscrew the lights near the screen and install a cheap dimmer so that lights at the back of the room can be on, but dimmed, so people can move about while watching 'the game'.
For sound, there are a ton of inexpensive options out there which can get you going. Onkyo offers some decent home theater in a box kits which can be similarly matched for around/under $500. Not earth shaking stuff here, but good quality at a reasonable price with 3D support.
For a projector itself, I would definitely plan about $1,000 for that if at all possible and get a new model like the BenQ W1070 or Optoma HD25. Both are under $1,000 and both will have a new lamp, new warranty, and offer 3D support which is good.
No in-wall cabling means that you are going to see all the wiring. If you want to go in-wall by paying someone, then you can expect that to be a couple thousand dollars of installation work by anyone who is part of a qualified professional company. Generally 2 guys at least 20 hours on that level of in-wall retro-fit wiring. Just something to keep in mind for the future I would expect.
This can all be done, by yourself, or with just a few hours of qualified help on certain items, for under $2,000 total.
W1070 - $1,000
Projector Mount - $50
Cables - $150
Receiver - $240 - Onkyo Refurb - http://www.accessories4less.com/make-a-store/item/ONKTXNR515/Onkyo-TX-NR515-7.2-Channel-Network-A/V-Receiver/1.html
Screen - $420 shipped
Speakers - $100 - http://www.monoprice.com/products/product.asp?c_id=109&cp_id=10906&cs_id=1090601&p_id=8247&seq=1&format=1#largeimage
That's $1,960 for everything and that's really light on the audio quality side, but certainly acceptable at lower volumes for what you are getting.