Customize comments shown

I would like to customize my comments shown on the main post. Particularly I would like it to be like a scroll down, showing approx. 4-5 comments – needing to scroll to see more. With an option to hide the comments & that when you click on the “leave a comment link” a dropdown should come down where you can leave your comments, (not that you should have to be taken to another page. Also if possible I would like it to show the total # of comments.

Thanks,
Irving