There was already a Custom Heist Track tutorial but it was not enough. This tutorial aims to explain what to do in much more detail.
Link to the tutorial itself can be found here.
40 GB free storage is recommended for all the external downloads (Unreal Engine, Visual Studio etc.)
Resources are included with the download. Thank @braidy08 (MoolahProject) and @WednesdayEnthusiast (repak.exe) for those.
Also huge thanks to @davidsebesta and @Cenrus for helping me through some of the issues I came across while making my first custom track.
Feel free to message me on discord about any suggestions/issues. (ID: ershiozer).