[support] Using drupal_http_request()

[Steve Edwards]

I've jumped in to finish up a site that someone else started (yee ha!), and I need to do two things with the user registration data:

1) Add some custom fields to the user registration form (i.e. address/city/state/zip, job title, occupation, company, etc.)
2) Use the data to add the user to an embedded mail list manager program (Oempro by Octeth).

Oempro can generate a script that adds the data to their database, and I can post to that script.  I modified the user 
registration form and added fields using hook_form_alter(), and that works fine.  The next step is to use hook_user() when $op == 
'insert' to post the user data to the Oempro script using drupal_http_request().  This brings up two issues:

1) How can I access the user data in hook_user()?  Is it part of $user at that point, or would it be in $edit?  Or another place?
2) How do I use drupal_http_request()?  Unfortunately I'm not very familiar with HTTP headers or with this function, so I'm not 
sure what to do.  For instance, do I put the form data (assuming I can get to it in hook_user()) to the $data parameter in array 
form?  And what do I put in the $header variable for a request like this?

Thanks.

Steve