Why can't you just put in in the "post-secondary institution" space on AMCAS (where you list your undergrad)? If you want to highlight it, though (i.e. explain the program, your reasons for enrolling, etc.), I would think putting it down as a post-secondary experience would be okay.
you'll have to put it in somewhere, since schools require all transcripts from every school you attended. No reason why putting it in post secondary experiences is a bad idea.
you should list it as a post-secondary institution and you should list your courses if you already know which ones you will be taking (for my program, we already know all the courses we will have to take). you DONT need to send a transcript because you can list it as a school you will attend but have not yet started at. It won't hinder your verification - I submitted my AMCAS July 10 and it was verified and processed by July 16.