S4S will take a Sitecore developer around 8 hours to install and configure basic the out-of-the-box functionality like the WFFM Mapping wizard. Time is required to configure the S4S settings and set up the Partner API user and access in the CRM.
If the Security Connector is required (login to Sitecore using credentials stored in Salesforce), it may take another 8 hours to install and configure the Salesforce package and create a suitable login control for the website.
The effort to install S4S EXM out-of-the-box functionality is up to two days. Much of this effort is around network and firewall configuration - ensuring Salesforce can securely access the Sitecore website using call outs.
FuseIT offers free install assistance to new customers which can significantly reduce the times above.