My advice... walk throught the Zumba door... it's the hardest part.
I feel like you need at least 3-5 classes for all of it to start making some sense. We have 2 main instructors throughout the week. One really kicks our butts... really a lot of thigh, butt, guts. Our other gal is really dancy. There is some cross over between the two gals.
I've watched a few other Zumba routines on You Tube. A couple are real extreme to me.. no way I could possibly move like that!!!

I am thrilled with my small town Iowa Zumba!!
I still don't like the shoes I'm wearing to class. Bring a towel and water bottle. I stood towards the back the first couple of times. I started just trying to get my feet to do what instructors were doing. Now, I've added arms.
One thing to remember... just move... HOWEVER... we all look completely different as we twist and turn. We laugh at ourselves A LOT! There are all ages, shapes and sizes in my class. It actually pretty inspiring to see different levels of fitness really enjoying the hour we share together...
Good luck and PLEASE go try it!!!!