OM namaH sAmavedAya
As this post describes, a form of the puruShasUkta is found in the sAmaveda, How is Purusha Sukta revealed in Samaveda?. Malola Kannan has also recited SrI sUktam from sAmaveda, but I cannot find the text of this. How is the SrIsUktam revealed in the sAmaveda?
I have now answered these two questions by myself:
This page is correct in saying that:
The basic text is expanded by adding new vowels, modifying some syllables and adding numerals at various points to denote the time duration and singing of those syllables. This version is called as gana and found only in books specialising in Samaveda singing.
This gAna text is the one performed like in the video above: see more examples of it on the pdf guide. It is very important for those who want to recite the sAmaveda traditionally. This book contains the gAna text for the first half. It seems to go up to sAman #640, out of 1875 total. It has the poorvArchika (585 sAmans) and AraNyakhAnda (55 sAmans). Where can the rest of the gAna text for the sAmaveda be found? This would contain mahAnAmnyArchikA and uttarArchikA, or sAmans #641-1875. There are many places where the basic sAmaveda text is found, but it is very hard to find the gAna.
My final question is shorter: what are some prayers to say before reciting the sAmaveda?