WebFace will receive one file or many files - the processing goes as follows:
(a) if all the required files are not present WebFace will reject the submission and send back an email to say a file or files are missing. In such a situation the submission is held but not sent on for marking. Thus you could make a submission by sending every file one by one using your coversheet, WebFace will keep sending back rejections until all the required files are present, it will then accept the submission and queue it for marking
(b) after the assignment is accepted you may make as many further submissions as you wish up to the cutoff date (of course if the resubmission is after the due date your grade will be penalised). A resubmission need only be the file or files you want to change (ie. resubmit) - if you send everything WebFace will reject those files which are the same as those already submitted with a message to say the files are not different. This is not a problem but simply a waste of effort.
Note that submitting just one changed file counts as submission, so making a minor change and resubmitting a single file after the due date will cause the assignment to be considered as late.
You should ALWAYS check the response WebFace returns carefully and ensure that what you wanted to happen did happen.
You can also view your latest submission (as WebFace has received it) at:
http://wfsubmit.its.monash.edu.au/index.cgi