At least two scholars argue that oral tales were an important source of the Povest′ vremennykh let (Stender-Petersen, Likhachev), but there is more to be said.
First two quick summary comments:
The focus of the presentation will be the process of converting oral tales to written form. While the oral originals are not available to us, it may still be possible to speculate about how the grammar of oral tales was modified as they were recorded. Dative absolutes (certainly) and other participles (probably) are the editor’s handiwork. The status of aorist and imperfect are, alas, difficult to determine, but at least the aorist was probably in the oral source.
More broadly, the concern here is pay attention to the etiology of the Povest´ vremennykh let—to the question of how it came into being.