For the first popup, why not use a decision task? display the questions in the tasks body text and the "I certify that the above list is completed" as the decision option.by the way - think about adding a rejection option, what if the list can not be completed?.
You can add the link to SAP PPM cProject in the SAP business workplace as an attachment to the task or create a z-object which default method is the link.
For second notification, if it's only a mail notification, you don't need a workflow task, you can send an email using classes cl_document_bcs/cl_bcs. you can of course use the send mail workflow step but it had troubles with sending links until the latest versions (see note 1966900).
