Looks like I never saw your question about how to use my script. Sorry about that!
My script assumes that you have the following columns/types:
Action (RTF) Context (RTF) Start Date (Date) Due Date (Date) Duration (RTF)
You can actually call them anything you like; they just have to be in that order and those types.
Then fill in your rows, using duration values like you would use in OmniFocus ("2w 3d 4h" should work fine, for example). Select the rows you want to import, and run the script. Those rows will appear in your Inbox, ready for further processing, conversion to projects, etc.
Note that my script doesn't do any date calculations, it just uses what you have in the OmniOutliner document. If you do want to adjust the dates of a bunch of items in OmniFocus, I suggest using Dan Byler's Defer script which can be found at http://bylr.net/files/omnifocus/
along with some other goodies.