There are definitely some good suggestions in here to get you started.
Something also to consider when building larger environment pieces like a building a good method to use would be modularity. One of the first modular tutorials I worked with was from 3D motive using UDK for a modular building. Tyler Wanlass goes through a whole process showing you how to build your assets layout the texture for the highest UV resolution by using a tiling texture. Using this type of method for texturing will give you the greatest resolution for your your uv space and keep from having to have such a large texture to make the object look great.
As everyone above has also mentions lightmaps are a very important task to set up when using Unreal. If you’re using a dynamically lit scene then, yes, you don’t need them, but if you are using static lighting you will absolutely need these to make your model look great!
Some tips and tutorials on setting up lightmaps (these are not specific to a particular software necessarily, but the concepts should help get you started and you can always ask questions when they arise):
While some of these reference UE3/UDK the concepts and theory is the same.
Epic’s Lightmapping documentation
World of Level Design - Lightmapping common problems and solutions
World of Level Design - Techniques and how to create a second UV in Maya (I know you dont have Maya but some good tips included!)
Hourcences - Lightmapping Basics
I hope this get’s you a good head start.