Bowing Down At Gurdawara (Guru Granth Sahib) Out Of Respect
Answer to the First Question : If not done as worship then it is not shirk but Haram in Islam and a major sin. We muslims have been strictly prohibited to not bow down or prostrate to others, even out of respect, the way we do for God in Salah. Answer to the Second Question : No it is not shirk. However, if the rituals involve polytheism of any kind, then such a participation should also be avoided.