Best way to group objects?

I am fairly new to Blender and 3D modeling and have a couple of questions about the best way to work within the program.

So far, I’ve attempted to model a power station (Pink Floyd fans will --hopefully(?)-- recognize it as Battersea). I constructed it first by creating one of the four towers, adding all of the components in that tower to a group, and then creating a group duplicate. I then constructed the rest of the station around the four towers after I had positioned them.

(Short video available here)

What I’m trying to do is build a library of models that I can import into other files as needed. I selected all of the components of the power station, including my group duplicates of the tower, and added them to a new group, PowerStation. I imported that into a new file. The problem with this is that when I try to scale the power station down to where I can add more components, the towers fly all over the screen (since they’re linked to the original tower). What is the best way of grouping objects into items that can be reused like that? Am I completely off on using Groups?

Also, in texturing, I find that I’m having problems plastering a brick texture onto the tower. It seems to want to apply it perfectly to the top of the cube, but the sides seem to be stretched. I’ve looked at UV Unwrap, but I’m not sure how to make a texture repeat once I load it in, and it seems to apply my texture to the entirety of the model and not just the one face, anyways.

Do any of you infinitely more advanced people have any advice for someone starting out?