If you copy and replace ALL of the files from 1.7.4 for the ones in 1.7.3.1, and you have not done any change at all in the code or database, if you go to public/upgrade, you would just need to select the latest version available, and that is it.
Please take into account that we have just realised that the automatic upgrade seems to have some issues in some environments, but we do not know yet if in all.
Best regards,
Francisco