Believe me, you'll have plenty of folks who can tell you they had to take a break and slow down at first. It comes with the territory. Really, don't worry about anyone else - even a level 1 class you've got different skill levels (newbies like you, those have done it longer, etc) so just worry about what you can do.
Hubby and I are starting back again - been missing training too much so we're gonna get right back in with the fitness classes so we won't take too much of a pounding in class
Just bring a towel, liquid and a fighting spirit and you'll be fine