VajrasUcikopanishad is a minor Upanishad which is attributed to SAma Veda.Ancient AcAryas have not quoted from this Upanishad.It is said to be popular mainly in Buddhist circles. There are stated to be different versions of this Upanishad.There is reference about vAlmiki, VyAsa, RishyaSrunga, JAmbuka, agastya, gautama and vasishtha in this Upanishad.
In a nutshell, VajrasUcikopanishad says that :
(1) JIva is not BrAhmaNa
(2) deha is not BrAhmaNa
(3) jAti is not BrAhmaNa
(4) jnAnam is not BrAhmaNa
(5) karma is not BrAhmaNa
(6) dhArmika is not BrAhmaNa
Finally in essence it means that one who has realized the non-dual Self is a brAhmanah --"advitIya Atma sAkshAtkAravaneva brAhmaNah!"
Assuming for a moment the authenticity of this minor Upanishad,regarding performance of samskAras only dharma SAstras would prevail over such texts as they only deal with the samskAras clearly from birth to death based on one's varNA and ASrama.