What would probably happen as I understand things would be something along these lines.
1) You look through the CDQ request forum and find a GM that isn't flogged like a plow horse, that fits your time schedule and ask to be put on thier CDQ schedule.
2) You exchange a few PM's with the GM about what, why, and when, and in your case who to change to, then you guys set up a date to run it.
3)On the CDQ you would most likely be challenged to justify why you want to change dieties with tests of faith and probably testing your knowledge of the dogma of the diety you intend to change to.
4) At some point in time on your CDQ as you shift from one diety to another you would lose your clerical abilities. This has to be handled by YOU in an RP fashion while in game, we could de-level you and make you a fighter for a week or two, then level you back up as a cleric of the new diety after the CDQ, but it's really much easier if the GM's can just trust that you want to do this and not use spells or domain powers untill they say so again.
5) Assuming you are successfull in your CDQ you will be shifted over to your new diety and be allowed to use your new spells and domains. I think the changing of domains is a bit trickier.
Hope thats helpfull, and mostly right.
Vyris