Yes, you definitely need a person to define the mappings across data sources. However, this is basically a one-time setup task; once the mappings have been established, new data from the existing databases can be continuously imported. I don't have any stats on how long this initial setup phase takes at real customer sites, and if I did I'm sure I couldn't share them publicly, but the goal is definitely for it to be something that doesn't require an entire team of consultants to deploy and babysit.
If you want to see the actual government product, and how it works, you can sign up at https://analyzethe.us/ for an account. This is a real live Palantir instance with real data from data.gov and it's open to the public.