adding hook to auto-mode-alist load

[Todd Wylie]

Greetings-

I recently changed my dot-file to automatically invoke 
paragraph-indent-text-mode for files of type *.plan like so:

(setq auto-mode-alist (cons '("\.plan$" . paragraph-indent-text-mode) 
auto-mode-alist))

But, I'd also like to load auto-fill-mode just for this type of file. Can I add 
a text-mode-hook for this setup?

Kind regards,
TW