I think that most of the tools needed to deal with losing a monogamous spouse would apply for losing a polyamorous partner. Some people may think the pain is less because you are with others, but from what I hear, it is not diminished.
It sounds like what you are looking for is sympathetic listening to your grief. It may help to tell the community here, but we don't know the situation as well as your partners do.
I think it is good to take time before you expose your heart against after it has been injured.
Sorry for your loss.