GPS in dashcams are not for directions, it is for loggin your speed and if wanted later to track your path on a map in some dedicated playback software like registrator viewer.
http://www.registratorviewer.com/index_en.html
A screen is good for initial lining up of the dashcam, and doing the settings, but its not really needed if you are good at eyeballing stuff.
You will want to have a 50/50 split of sky above horizon and road below, or maybe 60% road and 40 % sky, and then offcourse you will need it to point strait forward.
Some dashcams like the SG9665GC and others using a similar design you can only angle lens up and down, and then take care gluing the mount onto the windscreen so its level with the horizon.
Even if you are pretty drunk while installing i bet you will still get it right overall, and so you just might need a little tweaking on the followring trips after you have viewed your footage.
In my footage i have just about the lower 4 inches of my A-pillar in the footage so i use that to line up if needed.
Moving footage from camera to computer is best done by just taking out the SD card and put it in a card reader, or the adapter ( micro SD to USB ) that most likely come with the dashcam.
The optimal location for dashcams are up high and in the middle of the windscreen, but some new cars have a lot of stuff there so it might be out of the question.
If you plan on leaving the cam on the windscreen better go for a capasitor based camera, its not a price factor but it do narrow down the choices a little.
And Welcome to the Forum Glen, you have found the right place to be for dashcam information.