I do these classes hun and you will be fine. I hate cardio just in the gym too and love the classes but I just did the gym for a few weeks to get myself used to it again and then went back to classes at about 12 weeks. I won’t lie, it does feel odd to begin with and sometimes you will ache so just listen to your body and only do what you feel comfortable with. After a few weeks I felt back to normal again but i always found it easier to do morning classes as I didn’t ache as much, probably cos I hadn’t been using my arms all day. When I started back at body attack the constant arms above my head hurt a bit so I just eased that bit back in gradually and did the rest. Good luck for your op x