There is a good guide to replacing the sqlite and images file as the
first post in the first sticky, just be aware that you also have to delete the kepub directory for 1.8.x as well. You will not lose your preloaded books--but they will be in the kepub format, rather than living in the sqlite Db itself. That's a good thing
.
You will have to then sync your reader again. If the page numbering is off on your bookshelf, from previous syncs, then remove the books (rt click on the covers) from the shelf and then go into your "purchased books" list on the website,put checks next to the books you want on your reader, and then "bookmark" the books (top of purchased books ). Open the desktop application and update library.
The books you bookmarked on the website will appear on the shelves as new. Sync with your reader. You can then add your ePUB formatted books in via Adobe or Calibre.
This sounds more difficult than it actually is. You may also want to read the first post on the
Installation thread.
Initially, all the books you synced will appear in I'm Reading. That's OK. When you connect the reader to USB again, and choose manage, they wall slip into "Books" unless you opened them when they were in "I'm Reading".