Can I get an off-the-shelf system that includes FreeS/WAN?
There are a number of Linux distributions or firewall products which include FreeS/WAN. See this list. Using one of these, chosen to match your requirements and budget, may save you considerable time and effort. If you don’t know your requirements, start by reading Schneier’s Secrets and Lies. That gives the best overview of security issues I have seen. Then consider hiring a consultant (see next question) to help define your requirements.