being that it is a laptop, the atx-compliant psu's you listed won't work. i recommend something like the carnetix series-- a psu with a single output.
i don't even think it is worth gutting-- just leave it together, and use it as-is..
the momentary switch on the dash is not required-- any dc-dc psu designed for car use usually has a built in startup/shutdown controller. i still run one in case of emergency, but it is not a requirement.
for the screen, the minitouch is going to be a pretty good screen, but there are not any dd bezels for it. you would need to order the lilliput 701/629/669 to get a screen that is compatible with a standard double din opening.