I want to try for my first Ultra ending--Lawful.

First: Am I correct that I can get crowned Lawful as soon as I 1) see the Stone Circle on the map and 2) get the Medal from the HMV?

Second: If I want to Precrown a couple of times, am I correct that I should do it on a white altar before I go Chaotic, so as to avoid angering the Lawful god by doing it on a black altar and then later converting? (Or does piety decay make the white altars safe rapidly enough, if I only find a black altar in the early game?)

Third: Is it easy to convert the altar in Dwarftown as necessary, or would I tend to get sacrificed if I tried? (Assuming, of course, that I am not silly enough to make Dwarftown hostile.)