I wasn’t able to find a forum specific for this issue. I thought I’d like nothing but mountains but I miss all the other different biomes. Is there a way to change the spawn pattern of the biomes without losing what i already have? I’ve heard of recreating your world (and even though i don’t fully understand it), I’ve heard that you start completely over. I’ve heard of copying your world, but does that give me the opportunity to change the way my biomes spawn? I just want some sand, maybe some plains! I need a change of scenery but i love the house I’ve built. Halp
You can copy some or all the the chunks you've loaded from the world you have to a different world though that will give you weird and perhaps ugly cliffs at the borders between chunks generated in one world and ones generated in the other. You can either consider them a feature, spend time smoothing them out in game or find a world editor and use that to smooth them out.
Generate a new world with the settings you want, it might be worth your while to find a seed with mountains in the area you are copying to minimize how out of place the area you are copying (and its cliff borders) looks.
Now look in your Minecraft "saves" folder and find and open the folder for your current world (the folder isn't always called the same as the name you gave your world an easy way to help you find it is to sort the worlds in order of date/time), open the "region" folder, there you will find some files with names like r.-1.0.mca.
Now you need to figure out which regions (32X32 chunk areas) you want to copy, this can be figured out, divide the chunk coordinates of the chunks in the corners of the area you want to keep by 32 and throw away the decimals and you have the numbers in the file names. If you press F3 the chunk coordinates are the second set of three numbers on the line stating with "Chunk" 2 lines under the normal coordinates.
But I would suggest making it easy for yourself by creating an extra throwaway world, exploring the area that is equivalent to the area you want to keep in your current world, saving it, writing down the file names in its region folder and then copying the files with the same names from your current world to the new world. (You could use the new world to get the file names since the loaded parts will be overwritten anyways, then you'll have to use the coordinates to tell which part to explore since you won't recognize the area.)
Or if you want to copy everything you have explored in your current world you can just copy the whole "region" folder though I would suggest fully exploring a roughly circular or rectangular area to minimize the amount of cliffs at the chunk borders.
If all you really care about is the house you may be better off with a world editor but I'm the wrong person to ask about those.