If Opera doesn't (didn't) import everything on first run, then open the Run dialog or a command prompt and type
launcher.exe --presto-small-prefs-dir="C:\Documents and Settings\Steve\Application Data\Opera\Opera" --presto-large-prefs-dir="C:\Documents and Settings\Steve\Local Settings\Application Data\Opera\Opera"
... though obviously use the paths for your profiles instead of mine.
The above was posted in the Desktop Team blog something like 2 years ago; fortunately I did save it in my notes.
Opera/Blink does not overwrite Presto at all, I still have both available. Your desktop shortcut to Presto may be removed, but you can always re-create that.