I used a self-closing cabinet hinge because it has friction after you open it a certain amount, keeping it in place. The only thing is you have to be careful closing it because it wants to snap shut, really not a problem. The hinge also keeps the lid over an inch away from the bottom section, as you can see in the photo.
Keep your eye out for "friction" or "constant-torque" hinges. These will most likely be regular hinges and won't have that distance when open. Though I am happy with my hinge set-up.
The screen is a 4.3 inch rear-view screen(480x272), so it came with an RGB input. I cut away the extra cord that was for avi2. Of course the screen was 12v for cars, so I used the modification to jump off of the 5v resistor on the PCB board.
Like he did - http://www.skpang.co.uk/blog/archives/541
My LCD was quite a bit more difficult to get to the positive leg. It looked more computer assembled then the one from the link, but I soldered to what solder I could see. It was well under a milometer. After getting a good enough connection, I hot glued the wire in place because it is a portable device after all. You can splice it to the wire that powers your Pi but I installed both a switch for the battery(not needed as it turns out) and the ability to plug directly into an outlet. I rigged up a cord with a micro-USB and a jack that turns on the pi as soon as I plug it in. Now if I were to do it, I would have let the switch turn on power to the pi and LCD after it was plugged in. I was worried about having the battery get back-current but I believe USB is only one way.
I originally had the speaker wires right alongside the one cord coming from the monitor but after cutting the tiny speaker wire, I could not re-splice them so sadly I had to reroute the speaker wire. The speakers, by the way, are nothing special. a pair of tiny speakers I found at a dollar store. I didn't want an amplified speaker because of power, so they are good enough to hear if something is happening.
I liked your idea of the 5 inch monitor but ribbon cable scares me. I would suggest the 4.3 in over the 3.5 inch that you linked to but I would stress that initially I was shocked that the solder took and that it actually worked. Plus the monitor looked dead unless it had a signal going to it. Took me awhile to figure that out.
The screen I bought
http://www.amazon.com/gp/product/B006MP ... 06_s00_i00
Personally I think that having to wait for the keyboard will allow you to take your time. You get the Pi battery and monitor, get all those working well. Install qemu and set-up your image virtually before copying it to your sd card, meaning compile and install your emulators get everything set-up the way you want. Figure out your over-clock threshold too because you will want to overclock.
Long winded aren't I?