I would prepare a cover letter, research statement, and teaching statement for the application package. I guess if you include a statement of research, then the letter of application should be the same as a cover letter, basically, saying what position you are applying for, a general description of your interest in the position, your background in teaching and research, etc. one page is enough.

As for teaching statement, I would say something about my teaching philosophy (what's my teaching beliefs, goals, etc), and teaching experiences, and how well I performed in teaching, what I learned from the experiences, how I enjoyed it, etc. one or two pages.

Hope this helps!

Thx.