I had the same Stromberg-Carlson (it's made by Lippert) jack that you are asking about. It DOES have a manual override and a crank that comes with it. However, the motor on mine went bad after a few months, and Lippert was terrible to deal with.
I ended up replacing it with a Barker, same model as the one someone else sent a photo of. Motor issues aside, I like the Barker better. Runs quieter, has the manual override and light, as well as a 360-degree level on top. After about four years the switch went out on it, but the dealer replaced it for free and it is still kicking.
Regardless of the brand you choose, the power jack can make a world of difference if you use a weight distribution hitch. I have been in unlevel spots where I've had to jack my truck up with the rear almost off the ground in order to hook up the WDH, and hand-cranking would have been a real chore. For me, the power jack is a must-have.
2013 Surveyor SP220
2010 Silverado LT 5.3 V8
The world is a great book, of which those who never stir from home
read only a page. - St. Augustine