NTO you have been given great advise on here re your new yoga classes. Keep going, as others have said you did half the class, so well done you! If your class have no blocks, get your own and a new yoga mat, as it's nice to have your own, it does take 6 sessions to get the 'sticky' in the new mat, so a little practice at home will do the trick. Also a blanket is very handy, to roll up and sit on, instead of the block, to cushion your knees and hips, and head when you get onto the headstand not serious about the head stand lol.
I am a yoga teacher, and have students with many different health problems, including hip replacements, I always give variations and always say at the beginning to read your body and leave anything out that's not for you.
I've had cancer survivors, that were my students before, during and after, that have come just for the relaxation after their op and/or chemo, and from there, slowly back to being a regular yogi. Ages from children to 85yrs old and all fantastic!
Good luck xx