Many times they have generalized skills, but not a specific skill to run a machine. In a shop of our size that's what we are looking for. The important thing is to have a good relationship with your printer. A reputable firm will be honest with you and tell you if they can't do what you need. The key is the relationship and asking the right questions.
Proper planning is important, too.
If you have a big project coming up, talk to your printer and ask about the most cost effective ways of printing.