i did not start my 88 project yet, yes you can make it OEM, like your friend did. am not sure sure where he placed it, but if it's below where the old tape deck is you can easily get into accident by taking your eyes of the road, the alternative way would be shifting climate controls below.
The reason i will be using a flip up monitor is it's going to b directly on the level of my eyes, and there would be almost no glare
honestly if you just starting i would suggest flip since it's easy, but if you already got standard screen, the lower console is a piece of cake to work with, since it's easy removable. patience is the key
i want to see how your jetta comes out, since i am going to be doing an install in mine after i will rebuild an engine