Converting images fields to another fields

I think this is quite simple. I got a field that stores images (from 1 to couple items). This field is a field_attachment, and the problem is that it can't show the images. I need to convert them all to another field (f.e. field_image). The only small problem is, that the each node with that field_attachment got another one for the headline image - field_headline. When converting imahes to field_image, the script should pick one photo from field_attachment and set it as a field_headline. The rest images should put into the field_images. If the node got only one image_attachment it should be placed into the field_headline. Im running Drupal 7. The number of fields to convert (about 3500) images There is about 800 nodes Im not sure if the 'convert' is a good word. I need to 'move' the content from each field to another, and also delete the old - field_attachment. This is very urgent, and Im looking for programmer who already did it, and know all the issues etc.