Get the script to the show. You cannot write a paper on a play/musical and not read it.
The 1956 film version (Gordon McRae and Shirley Jones) is an okay adaptation and the ballet is there although Agnes' choreography is adapted by someone else. Nonetheless the film can show you the placement of the ballet.
There are R+H acting editions, a separate hard copy edition from Knopf and also the script is in a volume called "Six Plays By Rodgers and Hammerstein". Alas, the last two are out of print.
The first is available for sale at the Drama Book Shop (Google and go from there)
The other two would be for sale on abebooks.com which is a used book site. The single volume by Knopf is not cheap. The "Six Plays by R+H" volume is one of those books that is worth having in your library. If is is available at a reasonable price, buy it. You will keep it the rest of your theatre life, and others will be envious of you.
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