Surya Kriya is the name given to set of activities meant for activating Sun within you, as said by its planer Sadhguru. Isha yoga includes this kriya in their practice. You can learn it only with Isha Yoga and Sadhguru. I think it is not available free of cost.maybe I’m wrong. Only they can teach that process.
Surya Namaskar on other hand is a traditional method which includes seven asanas repeated to make a set of 24 steps. Each step involves exhalation /inhalation, concentrating on a particular part of the body ( Chakra) and chanting a Mantra, complete process balances nervous system, endocrinal glands system, blood circulation, stretching the whole body, toning of muscles, increases concentration, removes mental stress, regulates joints of the body etc.