Hi :)
The preview is located under the purchase files, under the "Download demo". The download button is a direct link to download. I think I have a preview PDF on every paid PDF.
I'm not sure how to check what files you've got already, but I think there is a link somewhere in your profile page. I often set the PDFs free for download. Is there some of them you want for free?
Yes, even though I source/steal most of the images and text from other places, the PDFs takes a very long time. The PC Engine, for example, took 6 months with (wild guess) 6-700 work hours. I don't want to think how long the PS2 PDF took. I decided to quit (for the third-fourth time) because I am very bad at time management, becoming obsessed with working on the PDF, which is not good for friends and family (not a complaint. I do enjoy, for the most part, creating these PDFs).
From Daniel :D