An educational publisher has contacted me for permission to use a blog post I wrote last year for an upcoming new edition of one of their textbooks.  The last time I was approached for permission to use something a company I worked for handled the rights negotiations.  Have any of you gone through this?  I've looked at some writers' resources (Writers Market, Writers Digest) and their permissions fee guidelines are all over the place.
The article is about 3200 words long.  I believe the textbook is targeted at undergraduate students in writing courses.  I have reached out to some friends of mine who publish in fiction markets but I don't know if any of them have textbook experience.

I know that textbook permissions can be a real nightmare for authors and publishers.  I would just like t charge a fair fee, not try to get rich.  I'm guessing a reasonable fee is probably in the hundreds of US dollars, not thousands (although the textbook could, if projected sales are met, gross more than a couple of million dollars).

Anyway, any timely suggestions would be appreciated.  I've asked the publisher what their permissions policy is but I suspect that my lack of a literary agent puts me at a disadvantage.  Haven't needed one for some time.