Keep reading, then.
You'll eventually learn that this ebay seller is a respected reseller within the community.
That regulated 12v source for the screen? It's the PC power supply, which is an M2-ATX.
I suggest you learn about what goes into a PC for vehicle installation rather than looking at products and asking if this is a good deal. By doing so, you will have a better understanding of your system and how it all works together. It will be a huge benefit when it comes time to troubleshoot problems.
Is this a good deal? Yes.
Is the seller reputable? Yes.