Creating content input form with custom theme (Drupal)

Question

I'm creating a site which I want to place content input form in custom themed template. I opted to do this because I wanted the whole site to be looked uniform. That said, I'm not sure as to what is the best approach to do this. Is it proper to invoke hook_insert/delete/update and hook_perm/hook_access by myself or is there anyway I can still use my custom theme and write a code in a way that drupal would take care of invoking appropriate hooks accordingly? Thanks in advance

PS : I'm on drupal 6.x