I have more to say about the Sibyl's Prophecy - a lot more, otherwise known as chapter one of Printing and Prophecy. I'd better stop here.
The essential scholarly work on the Sibyl's Prophecy is Frieder Schanze, "Wieder einmal das 'Fragment vom Weltgericht' - Bermerkungen und Materialien zur 'Sybillenweissagung,'" Gutenberg-Jahrbuch 75 (2000): 42–63. Schanze's article provides a list of all known manuscripts and printed editions, discusses some of the improbable things that have been asserted about the history and meaning of the text, and points out several important things that remain unknown. We still don't have a critical edition or a complete understanding of how all the printed editions and manuscripts are related.
Schanze's article provides the best accessible facsimile of Gutenberg's edition I know of. I don't know of any digital edition available online. After Gutenberg's edition, the next edition of the Sibyllenweissagung didn't appear until 1472-74 (following Schanze's dating), and then five editions appeared in 1491-93. One of these later incunable editions (ISTC is00492620, GW M41985) is available in facsimile from the Bayerische Staatsbibliothek. So the release this week of a facsimile from e-rara.ch of Flach's edition (ISTC is00492550, GW M41983) fills a notable digital hole in the history of an important text.