that seems likea good deal. i have never priced a in-dash 7 inch lcd screen but it seems like a good price for one.
as for your other questions.
1) vga inputs are only needed really if you're going to hook up a computer to the screen. vga will give you a lot sharper picture then a tv/out will that is hooked up via rca cable. Give it a try yourself, if you have a tv/out video card. Hook it up to your tv and look and the different from the tv to the monitor. A lot of us use GPS and such in the car where we want clear crisp text. a vga screen will give us readable text while an rca input screen is very blurry.
2) touchscreens are also for the computer. they just act like a mouse. I don't like them since they are just as bad of a distraction as a mouse in my opinion. I like to us an IRman which is a remote.
3) that is a 7inch wide? vga screen. its a very good price. A lot of people on these boards buy them if they want something you don't have to build yourself.