Charles Ranhofer's The Epicurean has quite a dissertation on turtle, or terrapin as he refers to them and several recipes. I'll attempt to scan and post as re-typing the entire thing would be too time consuming.
What I can tell you so far is that he recommends letting them swim in tepid water for about half an hour, then change the water several times.
Rinse and scald in boiling water until the skin (on head and feet) can be easily removed. The meat attached to the upper shell is the most delicate and flavorful.
Then simmer or steam for about forty five minutes. The feet meat should yield easily to pressure when done. Cool. , Remove the shell then, "the lights, entrails, head, tail, claws, heart, muscles and gall bladder to be thrown away." Watch out for the gall bladder. Don't pierce it. Save the liver.
Sherry, Madeira and white wine feature in most of his recipes. Also served in thickened broth of one kind or another after substantial cooking times. Hard cooked eggs, sliced or sieved feature in many recipes as well.
The older versions of Joy of Cooking have a recipe for turtle. Not too far from Ranhofers' but no discussion on cleaning fresh turtle.
According to Ranhofer, the winter months are the best time for turtles, ending about March. I don't know if that's still relevant.
If I can find any more I'll post an update.
