This module is in beta, and does not support purchases from more than one seller at a time. I can imagine a later fix that integrates the order-total by using http://www.ubercart.org/project/uc_adaptive_paypal as a reference for implementation.
Due to the potential sensitivity of the papyal API-data for merchants, I chose to use the crypt module to encrypt the data. Please place a file named "mp_paypal.key" with your encryption-key in it. This file should be placed inside the SAME directory that you set the "Card number encryption key filepath" in the admin/store/settings/payment/edit/methods page.
Instead of having only one spot to add/edit paypal API information about WPP, you now have two spots:
1.)The admin/store/settings/payment/edit/gateways will still have admin-configured settings about the payment gateway.
2.) The user-profile will now display a link to change their own API information, or if your the admin (and don't want sellers adding this themselves), as an admin you can edit their API information from their user profile page.
Once installed, a new permission is added called "administer own paypal" , set this permission to sellers you want to be allowed to update their own API information.
1.)Testing with WPP requires a specific request for this type of test account from paypal.
2.)Currently only supports WPP
Hope this is useful to someone, and I welcome any contributions/testing.