Before I go and give it a whirl at explaining this, have you considered using a CMS? vBadvanced allows you to pull PHP files in a "module" type of setting. Since vBadvaced is already 100% integrated with vBulletin, this would likely be the easiest way to do this.
It allows you to create pages, in unlimited quantities, using external or internal files and templates. The url would read:
index.php?page=YourPageName
and it would be automatically added to a vb page! For more information on this, check out:
http://www.vbadvanced.com
Did I mention it is free? lol
With 100+ pages to add, no matter how you go about doing this, you are looking at some work. I believe this would be the easiest method though.