Widgets questions

Hello,

I would like to know if is posible to show one widget only in one post for example: post 1532. I know there is 1 plugin (Widget Context) that allow do this, but it does not work with my theme.

I want to add 1 iframe but I don′t know how.

I was cheking and find that I could add something like this:

<?php if is_single( 'beef-stew' ) ?>

I had installed WP PHP widget, but.. Can I use this?, can I add iframe anywhere here?, can any help me to do this??