Throw up a post over in the home improvement board. There are lots of handy guys in here that could help get you started. There is probably someone in your area who may even help you with it if you are willing to throw in a hot lunch and a couple of beers. The biggest thing is getting the floor put together for strength and getting the walls straight. After that it goes pretty quick. If you can use a screw gun and a skil saw you can build your own fish house.
If you want an actual "blueprint", Lowes, Menards or Home Depot should have storage shed plans. You may want to substitute in some slightly ligher materials to make it easier to move on and off the lake.
I have just enough wood working knowledge to be dangerous and built both a permanent fish house and a storage shed this year, both of which turned out to be pretty presentable IMO. The fit and finish is not what would come from a professional but as one of my friends says "we ain't building watches".
So many lakes, so little time.