Yes, a great deal will need to be done. First of all, the list of security standards are here: https://www.pcisecuritystandards.org/security_standards/
This entire list applies to all size environments. The only thing that changes depending on how many credit card numbers you process and whether or not you are a service provider for other retail storefronts is the level of audit that must be performed on a regular basis.
If you've never been through the process before, and your environment doesn't require a third-party audit, I recommend going through at least one audit the first time to have some assurance that you've followed the guidelines listed in the Security Standards documents.
If at all possible, I highly recommend avoiding PCI compliance requirements by using a third-party payment processor. Full compliance is a very expensive endeavor.