So, currently there is no mod pack/release for people to mod, I know it will take a while and some people do want to mod the game.
ALSO THIS IS CODE ONLY, FOR SOME STUFF LIKE CHANGING WHAT SOUND PLAYS AND ETC
First, you want to get a decompiler, I would recommend https://github.com/0xd4d/dnSpy
Second, once installed you want to run it and find Assembly-CSharp.dll. which in most cases CB v0.5.6.2 (Windows 64-bit)\Containment Breach_Data\Managed.
Third, drag that into, and of course you are now in! You can change most of the code.
Sorry if you expected more, if you need any help just ask.