Would say they are very good for explosiveness but not necessary if a alternative can be used, e.g. kettle bell snatch. The Oly lifts are very technical and if you are struggling with the technique it might be safer to find an alternative explosive movement that you can do - as long as it improves explosiveness.
I have found Max Jones' book very useful. He has one for each event.
Got the Discus one and it is wonderful. Started throwing in October at the age of 30 so completely know what it is to start later in life. Best decision I have ever made - helped really focus at the gym with weights etc - I hope it is going well!
Congrats to her and her wife! Great to have a LGBT role model in throwing!