How to assign drupal webform to drupal node/block?
I suggest using the Webform Block module. It is stable and compatible with Drupal 6.


  Allows embedding a webform node into a block which can be positioned in any block region (theme space permitting).
  
  Handles redirecting back to the current page on validation errors.
  
  A good use for this is to add a site wide contact form inline on your pages, such as in the footer or sidebar.