How do you programmatically modify a programmatically created content type? I'm creating a Drupal 7 site that has many content types which are defined programmatically. It is quite likely that, after launch, I will be required to slightly modify some of the content types. During development, whenever I need to make a change, I just uninstall the module, make the changes in code, and reinstall it. In a production environment where the data needs to be kept stable, this is clearly not acceptable. 

How can I modify one of my existing content types programmatically? Also, how would I apply this update?
http://api.drupal.org/api/drupal/modules--field--field.crud.inc/function/field_update_field/7
http://api.drupal.org/api/drupal/modules--field--field.crud.inc/function/field_update_instance/7


Open WWWROOT/profiles/standard/standard.install (starting from line 199)
Profile install creates basic content types (like Article and Basic page)