You dont need any scripting info for modifying a campaign. All you need to do is create/edit one of the mct files to create a campaign of your choice. The mct files are found in your Campaigns folder, each one of them corresponds to one of the single player campaigns you see at the single player campaign selector screen.
Its best to make a copy of an existing mct file, and then just modify it. The missions used in the campaign are listed in the mct file, simply remove the unique campaign missions if you dont want to use them. The file itself is relatively self explanatory, also be sure to rename the camapign to something like "My campaign" or some other appropriate name so you discern which one it is at the campaign selector screen.
If you would like a copy of OP, I believe CUGS has as supply of them for sale for around 10$ each (I think). Contact DIF-Josh for more info.