You can only do half of what you want to do. You can have the form return all the information to an email address (don't think you even need JS to do this), but JavsScript cannot read/write to files. This means that any data you want to store cannot be stored as there's no way to store it.
For what you want to do, you will need to use a serverside language (my favourite is PHP) and then use this to do everything that you want i.e. Send the email and save the data.
Have a look at this post
(you may want to have a look at the posts above it to put it into context) for more information. There are plenty of tutorials around on how to do the things you're looking for, so try google too
Hope that points you in the right direction