Misconceptions of the paper guide to Skyrim, the original edition (Steal statue of Dibella&Heart of Dibella)
The way they said it in the paper guide that I have, is that it is imposible to do both, to steal the statue and to get the quest of Heart of Dibella. Maybe not when you trying to do it all at once. If after you successfully stolen the statue and then talk to Hamal and accept the quest, the statue gets removed. If you try to take the statue after the quest Pristesses become hostile. If instead of agreeing to the quest you kill all of the Pristesses to get the statue, the outcome is obvious.
However, I found a different way to accomplish both. My Nord Thief (At that moment), successfully snuck past the girls into the back room and snatched the statue. At that point, they started to come back in the room, so he snuck into the hall in between and hid in the corner. All of the women, went right by him without noticing him. He then snuck the same way he came there. The only problem, it seemed that they have re locked the doors to the inner sanctum and he had to re open the expert level lock again. He then hurried back to Degaine, sold him the statue and then went back into the temple just to get caugh by Hamal and accept the quest to bring the Sybil of Dibella back.
Long story short, he brough the Sybil and after accepting the blessing of Dibella and becoming an Agent of Dibella, he was able to marry any of the Pristesses that were marriagiable, but not before he drank from the pool. Oh and the only thing he used, was his thieves guild armor (upgraded cuiras from Tanilia) and a Muffle spell.
Seems like no one considered to get the statue to Degaine first and then return to the temble for the chance to get the quest as well. At least no quide considered it, or they made you believe it's impossible on purpose. I am sure there are people who tried getting both, the same way I was able to. Oh and after marriage, the Priestesses really have no life. Even if you tell them to live in your house at temple of Mara, they still will go back to temple of Dibella and never will actually show up in your house. Except somehow, you are still getting lover's comfort anyways if you sleep in your bed. I had my Nord marry Orla, but didn't play enough to actually find her in the house. After marriage, she went straight out of Riften, when he had a house in Riften and they agreed that for the sake of his daugher, they are going to live in his house. He slept and got lovers confort, but I haven't seen Orla appear in the house.