For something that is easier to see in sunlight, I would say you probably want a transreflective (glossy) screen. These do produce some glare issues due to the glossy coating, but are usually much brighter in sunlight than transmissive (matte) displays. Some matte displays are okay in direct sunlight, but most really fade out.
If it is going to be mounted in a vehicle, you probably want a 15.4" or 15" screen. 17" notebooks are HUGE and you might have difficulty mounting it. In terms of screen resolution, it depends on your usage. Higher resoulutions like SXGA+/WSXGA+ or UXGA/WUXGA are nice for regular usage, but if you're trying to read text a couple feet away from the screen it will probably be difficult to make out. I wouldn't go with any type of UXGA screen in that setting, SXGA+/WSXGA+ at most. In fact, a regular XGA/WXGA might be ideal as it would be VERY easy to read. If you need to do a lot of browsing in your usage, you will have to scroll more as less text will fit on a screen, but it will be very easily readable.