Here you go.
If you use the Speidel spigots use the Chrome ones not the plastic ones. If you use the norcal ones, make sure you buy the plastic cap and the silicone wrap. I bought the ball valves independently for much cheaper and added adaptors for hoses. If you want to ferment with the spigot, just sanitize it like anything else and then cover the exit in sanitized foil.
Fill by gravity. Insert a gas quick disconnect once everything is connected and the beer going down will push the gas off the keg through the disconnect. I imagine that in addition to gravity, you will push from the top with CO2 in this case.
You can easily see the yeast/ trub level in the speidel. If it is below the level of the spigot, then transfer until you reach the level of the yeast. If it is above the level of the spigot, incline the Speidel backwards until it is below the level of the Speidel. Use something that won't slide.
I would cut the keg gas-in tube so that the beer can reach the top of the keg.
If you have more beer than the keg can take, then beer will eventually come out of the disconnect; at tha point get the disconnect out and you are done.
Keep in mind that your keg is filled to the top, so get some beer out before you connect gas or make sure gas has pressure, otherwise beer will come into the gas line.
I have done 300 beers this way, so if it can happen, I have seen it :-)