Need information on use of Salesforce certificate in SAP PI

Dear Experts,

We are integrating Salesforce SFDC to ECC using SAP PI 7.4 dual stack.

There are few questions that I have .Please answer them.

1)For interacting with SFDC without any encryption. Do we need certificate from SFDC to be deployed in SAP PI ?

2) I've been given one .crt file by SFDC team .Will that be enough ? Because in past when I worked in Successfactors I used there website to extract three certs and deployed in NWA. So not sure if one cert from SFDC is enough?

3)SFDC resource who gave me this .crt file says its self signed Certificate. Will it be ok? or does it need to be CA authorized?

4)In anycase once we receive the right cert.Can we follow the method given in the below like to deploy the cert?

http://scn.sap.com/community/pi-and-soa-middleware/blog/2013/01/06/how-to-load-keys-and-certificates-in-sap-pi-sap-po-key-storage

5)Do I need to ask the SFDC team for the cert or I can extract it from there website ? If possible can someone guide me on that ?

Thanks in advance