You need to know more than the person you're freelancing to... Since you've had a few years in a related field and built up some contacts you should be good to

You need to know more than the person you're freelancing to... Since you've had a few years in a related field and built up some contacts you should be good to go (as long as you have a good rep with them). Let them know you are offering a new service, and get some info up. No matter what you're going to be learning new stuff the whole time, so you may as well just start now!