Hi Emma,
I am new here, but I will give it my best shot.
From what I can see of the village map, all the buildings were made of cubes, so you do have to do one or two buildings at a time. There is a pretty easy way to do this, though.
Go into edit mode and get a view of the building you want to delete, from the top.
If you left click on the lower left block of the roof line, then right click on the upper right corner of the roof line, you will have the blocks on that level selected.
Now rather than take it to the ground, using your mouse scroll wheel, come up until you have a big rectangular shape that includes all the blocks at the peak. It will look pretty strange, because of all the different textures.
Now, take your mouse wheel and start moving it in reverse, so that the blocks are going down to the ground. At ground level you can stop.
It actually works pretty fast. One building will be gone in a few seconds, then just move onto the next. You can wait to re-texture the terrain until you are all done.
If you want grass, just select all the blocks that are not grass textured, using the same left mouse and right mouse click method. You can also just select an even larger area that includes some of the grass, if you need to. Choose your texture and you are done, except for maybe a little grooming of the hillsides around where the building was seated.
A Note: Save your work, after you remove every building, just in case you make a mistake. That way, you have a backup of every step of the way.
Hope this helps!
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