Add a Term to a Taxonomy via Forms

Hello,

I had found this code that was a bit older but claimed to do what I wanted:

function hyp_tag_to_taxonomy( $form ){
     $id = $form['post_id'];
     $raw_tag_list = $form['input_7'];
     $tag_array = explode(',', $raw_tag_list);
     wp_set_object_terms( $id, $tag, 'TAXONOMY' , true);

}

add_action( 'gform_post_submission', 'hyp_tag_to_taxonomy' );

Essentially, I want one of my form fields to be able to inject a taxonomy term into a specific taxonomy.

Actually, what I'd REALLY love is a field that does 2 things..... Uses some sort of auto-complete to query all the current terms for a specific taxonomy and give those as suggestions for the field.... if then the term doesn't exist, it add the new term... but I'm sure that's a much larger request ;)

I'd LOVE this as well.