S&S are different for everyone. Just go in without any expectations. I did my on a Monday, by the following Monday I went into labour..not sure if it was because of it. Worth getting it done.
The main reason I'd like to go to a mothers group is to find out best GPs, pediatricians etc in the area - find out who they're using etc. also like to go to a mum's and bubs workout when she is a few weeks older.