Lise, I didn't mean to be cryptic.
But the very question "How we know Milarepa was enlightened?" led me to the bigger question.
If one reads Milarepa's life story, and his songs, one can get a very good idea of his state of mind, and his state of realization, I think. However, some people may feel that his life story is just too fabulous to believe--at one point, for example, he shelters inside a conch shell!
So, given those accounts, some would feel devotion and faith.....some, on the other hand, would discount everything they'd heard about the White Cotton Clad One.
Traditionally, all Tibetan Buddhist lineages see Milarepa as the greatest Yogi from the land of Tibet. He is the exemplar, if you will. I'm going to make a bold statement, that Milarepa is the third most important figure in the Tibetan Buddhist World, behind only Buddha Sakyamuni and Guru Padmasambhava. In my opinion, he also had the best sense of humor af all of them!
I think he "attained" that position due to some sort of special qualities, don't you?
Especially given his not-so-savory past....??? Perhaps these are things you can discuss with your husband.
Now, from a personal point of view, if one knows some of the Dharma, and reads and studies some of Milarepa's songs, one can be convinced, I think, that he was a great and skillful teacher, as well as a great yogi. Khenpo Tsultrim Gyamtso, in particular, used several of Mila's songs as pith instructions, from which he taught a wide variety of topics central to the Karma Kagyu understanding of Madhyamika, Yogacara, Tantric practice of the two stages, and Mahamudra.
The most common Milarepa practice sadhana, and the corresponding empowerment, come from Jamgon Kongtrul Lodro Taye's collected writings. This is a profound Practice of the Guru. Entering into this practice with devotion and yearning can be very effective. I do think some teachers bestow this as a "blessing," without any practice commitments, but it's best to ask beforehand, as Caz points out.
May we all benefit from the words of the Cotton Clad One who Attained Enlightenment in this very life!