Haven't done specifically PeopleSoft WS, however it should not be different than consuming any other Web Services (REST or SOAP).
General practice is, Create Configuration Group and Configuration Items, as one to many relationship entities. Store the WeSb Service Connection String and account's credentials in Configuration Items (you can store the password as Base64String ). Once settings
are configured properly, read it dynamically using Configuration Group Key name in Plug-in code.
Let us know if you have any specific concerns.
MaKeer|<a href="http://wp.me/1AkRL" target="_blank">myencounterwithcrm.wordpress.com </a>