Question 1. no. It uses a subdomain of the node, Shared SSL basically means we have purchased a wildcard ssl and subdomains can be protected, extending to multiple domains is not possible without error, which you don't want with SSL.
Question 2: If you don't know the original PKey and CSR yes for the most part you aren't in a good place, these should always be stored on file. So yes requesting a new CSR will regenerate those and need existing SSL off, these can generally be done quickly now so if you were to send a ticket and generate the new CSR/PKey, input to the ssl provider, get their response we could see to it and help you get the SSL up quickly with as little down as possible.