When player clicks on a "Start game" option, the following process happens:
1. Warband proceeds to menu item "start_game_0". This behavior is hardcoded.
2. Module code asks player a number of questions to generate player's character biography and starting stats.
3. Module code opens character screen for player for the first time.
4. When character screen is opened for the first time, Warband forces the player to generate his character, distributing the points and generating a face. This behavior is hardcoded.
5. After character generation is complete, Warband automatically proceeds to menu item "start_phase_2". Again, this behavior is hardcoded.
6. Module code then asks player where he wishes to start the game, teleports him to appropriate town and starts the tutorial quest.
So essentially, if you want to get rid of the tutorial quest, find "start_phase_2" menu in the module_game_menus.py and trace the code from there. By that time player's character is already created and finalized, so you just need to remove the starting mission and simply drop player's party in the vicinity of whatever town he chooses. Or do something else depending on your mod's needs.