with fish and smaller animals I usually let the pile "cook" for a month then turn it every other day after that until its cold and the materials are unrecognizable. Make sure your pile is large enough....mine are about 5 feet high and 5 feet wide.
I have composted fish and its turns out just fine. Once the pile gets hot they disappear within a couple of days. I have also done this with roadkill deer, foxes, birds, squirrels, and rabbits. There is no smell whatsoever and i never had a issue with critters. With fish you could also make homemade fish emulsion or just do it the indian way and bury it in holes during planting time.
there is a design for a earthship hut....its much smaller and round. It doesn't have a greenhouse but it does collect rainwater and its earth sheltered. Cost is around $2500 USD to build so very cheap. You might want to try that first before doing a whole one plus you will gain some experience on how to build them. Only downside is that they don't stay as warm as an earthship with a greenhouse. Still the lowest the temp will go inside the hut is that of the earth around 55 degrees or so.