you can always use winterboard to apply sound themes, but it really only works if you create a custom theme. if you are wanting to change just a few things.......
then check this out
was using that in 2.2.1 days but i'm sure the file structure is the same.... i think
this can also be applied to emails as well all you need to do is find the file that says email... i think
remember to alway back up your original files... easiest way to do so is by just typing bak in the file name
example: original file=>email.caf backup file=> email_bak.caf
that way if anything goes wrong all you have to do is delete the _bak and you'll have your original file to use still...
hope this helps