just get prerealse and create a world then what you want to do is leave every thing alone but you can build you house in a tree and other stuff and then you have to..... MAKE SURE YOU HAVE THE MINECRAFT FROM BIN IN FLODER OF .MINECRAFT then take minecraft out and put in the other minecraft you got and you have the prerealse so then you want to find a jungle boime then log out and take the prerealse but if you want to keep the prerealse save in and then put the minecraft the one you toke out put it back and then you have a jungle boime the wood will just go back to forest wood and leaves all of the new wood and you have a jungle boime for 1.1.0 and you can use it for a server map so HAVE FUN with your new map