For the DL, you'll need to download a few mods (Complex is a good example to work with, I'd say) and the community modding tools. Look for unfBig, which will allow you to extract the .big format in which all Workshop mods are. Unpack it in the \Data\ folder of your game. Get RODOH, HODOR and DAEnerys if you want to work with the actual files for the ships (the textured models and their joints, markers, etc.). Beyond that, a code editor like Notepad++ will help you to edit the numerous code files. Look for the functions and their uses there: http://hw2bsg.org/wiki.hw2.info/FunctionReference.html (you'll find a crapload of useful information there)
If you're not going crazy with 3D and texture edition, it should remain a relatively small endeavour overall.
Get your modded files with the proper hierarchy in the \Data\ folder and launch the game by making a shortcut to the exe file of the game (in \Bin\Release). Right-click that shortcut and add to the target the following stuff (dash included):
Whenever it crashes on your face, go to \Bin\Release\ and look for the file called HWRM.log, where you'll find, with some luck, what made your game crash.