Is trigeminal neuralgia very serious?

YES! If not treated. Tn is a specific name to a type of facial pain. It can take a few doctors visits to get a final ruling. Don't wait it is not cancer but the pain can make you wish you were dead! Think flesh/tissue and not nerves for face pain! Begin a self-care wellness program of vits, magnesium glycinate, sleep hygiene, self/pro massage, chiropractor, heat, epsom soaking, stretching. I use acupuncture!
Sometimes. If untreated, it may become very severe and people may become very depressed. Best to treat earlier and opt for not only medical pain relief, but also a cure (especially if medication does not completely control or results in unacceptable side effects). Important to see a specialist.
No. It can be very painful, to the point of causing difficulty speaking or eating, and it can sometimes be caused by a tumor, but trigeminal neuralgia itself is not life threatening, not associated with other neurologic dysfunction, and rarely causes significant disability.