one of the first requirements for PCI Compliance is that the site be SSL enabled to ensure a secure transaction. While it is possible to have SSL Installed on a shared server, it is problematic.
The first place to start for information is the PCI Security Council site:
https://www.pcisecuritystandards.org/hardware_software/
Through Google, there are many resources that can be found for information on PCI Compliance, here is one i found through a quick search:
http://www.pcicomplianceguide.org/
there are many others