Zephan,
don't ever put passwords into your code. If it's there, sooner or later someone will find it and use it.
As to hiding the code from other users, that's easy.
Create a new user, called Zephan and grant privileges to create a package. Log in as zephan and create your package. Then grant execute on Zephan to the other users.
Other users will be able to invoke the functions and/or procedures in the package specification, but will not be able to 'see' the package body, thus protecting your code.
I repeat, never put passwords in code.
Regards
T