I am an InDesign guru. I'm the guy they ask to teach "non-designers" on how to use InDesign. As such, I know the basics, the ins and outs, the shortcuts, the easiest, fastest, and most efficient methods on how to bring in content, format it (that you have a template is great), and make sure it's press-ready.
A note on your template. I'm assuming you have the page setup, margins, bleeds, columns, paragraph styles, character styles, graphic styles, master pages, etc.
Since you want a math textbook, I'll work in math composer and have a math teacher (friend of mine) triple-check my work. I'm sure accuracy is a top priority for your project.
As a last note. I once took a client's 6000+ entry Excel worksheet and used all the tricks up my sleeve (formatting in Excel, Find and Replace, Paragraph Styles, Character Styles, Master Pages, etc.) to create a 200+ page phone directory. That's the kind of experience and expertise I can bring to your project.
Good luck in your search.