This is maybe the largest scene you have ever made, in terms of details and number of objects. So we will take some time to learn how to organize ourselves in order to have a more manageable scene.
One interesting thing that Blender has to offer is the grouping tool. Let's see how it is working:
Using groups
Groups are very useful as they allow you to organize a scene better. You can see all the groups that are in a scene in the outline by changing the All Scenes drop-down menu to Groups. Here you can select them, disable their render, and hide them. You can also select one object that is part of a group in 3D view and press Shift + G and select Group to select all the other objects of the same group. You can add or remove an object from a specific group in the Object tab of the Properties editor under the Groups subpanel.
Another thing that can help your scene organization are the layers. They are located in the 3D View header. You can move objects on specific layers with the M key. A popup will show you all the layers. You can move an object on multiple layers by pressing shift and selecting the layers that you want. The layers that have objects are marked with a little circle. You can display multiple layers at a time by pressing the Shift key and clicking on them in the header bar. Note that you can also see the layers in Scene tab of the Properties editor. In our case, the house is on layer one and the other elements on layer two.
Layer one is selected, but we can see that there are objects on layer two