I'm happy to help. Are you familiar with creating a disk image for the pi? The octoprint image just needs to be put on an SD card using regular means for your os.
Use a good sized SD card (16-32gigz) since all of your print files and time-lapse files will get saved to that card as well.
Follow the steps to set up your Wi-Fi password, and to expand the file system to use the entire SD card.
I keep my Raspberry Pi external to the printer, so it can be turned on and off as needed, and the wireless Wi-Fi card can be pulled out to be reset if needed.
I think the idea of powering the Raspberry Pi off of the printer itself is silly, there are times when you want to be able to turn your printer off to work on it, but still have the octoprint server running. You always want to shut down a Linux based operating system with the proper commands, not just kill the power to it.
I would recommend just printing yourself a nice case for the Raspberry Pi, and have it external to the printer, powered off of a 2amp 5V wall charger.
As far as the webcam goes, I leave my lid open with the webcam attached to the top of the printer. That way, it is always shining down on the print. Where you put the webcam will depend on what angle you want to see your print. I angle it so that the camera looks exactly like the gcode that you see on octoprint.
Any cheap USB webcam will work. The one I have is at least 8 years old, and is by no means high definition.
Da Vinci 1.0a. Repetier 0.92. E3D V6. Titan Extruder. Sllic3r. Octoprint on Raspberry Pi B+.