[support] disable edit of submitted nodes/content

Hi, I am using Drupal 6. I have created a few custom CCK content types. I am trying to have a system where authenticated users can submit content/ideas. These ideas should be somehow assigned to a few moderators. Initial investigations tell me that there are some modules (modr8 and similar stuff). I haven't tried these yet. To start with I want the admin to be able to freeze/ totally disable the edit tab/ disable individual cck fields in the cck contenty type for each content node created by the user. How can this be achieved? I have tried Rules and Content access but couldn't really work around them. Are these the correct things to look at? All help appreciated. Regards - Ben