run powershell scripts with service account + profile

I want to run powershell scripts with a service account. That's no problem exept that the objects i want to use i have to add-pssnapin in the profile to get some cmd-lets to work. Do i need a custom profile wih i can refere to when i run scripts with the service account?
And furthermore i need to read a file that will have a username and password, so i can login in to some services. How can i protect the file or encrypt it so i can use it in the scripts?
 
Thanks in advance.

Your service account will likely need a profile script just like a regular user.  Or simply add the commands to your script. Is this part of a scheduled task?  How is the service account running the script? If you don't have a "real" person running the script then there's no way to enter a password. If you absolutely have to embed credentials, then consider packaging your script with a product like PrimalScript.