Hello,
There are many tutorials around, but it can be daunting a bit because much of the information is 2 years old, some of the tutorials were made before CA explained the system some of them after it.
As a rule of thumb, don't get in to ways of having to unpack and repack the pack files, while it maybe good to take a look to understand the evolution of modding and research, breakthroughs people have done, there are a couple of good tools that can do the modding without unpacking and repacking the files manually.
I started with this one (the first link bellow), and found it quite helpful to understand the new way of modding. I been doing mods since STW myself, but until recently moded only up to RTW, the "old fashion way", then TW game engines changed and it became quite a different ball game which I beleive may have discouraged some modders (at least it discouraged me heh).
Yet, it seems like with ETW, it may actually be better, provided one has the appropriate tools, which of course requires people who can code them, which means that it is still not as accessible as previous TW games, since it is no longer about opening a file with notepad and starting to do modifications.
But it is what it is and we just have to go along with it, fortunately people who are making tools are plentiful here and the tools are good, so along with that collaboration of modders, CA actually found the best way there could be to do them in a safe way limiting possible issues and errors, and our thanks go equally to them as well the Tool Makers and Tutorial Writers.
So I suggest this thread to start with:
http://www.twcenter.net/forums/showthread.php?t=291282
To understand the Architecture of modding I suggest this thread:
http://www.twcenter.net/forums/showthread.php?t=239487
The tools I use are:
ESFeditor, DBEditor, PackFileManager and the ModManager (albeit you can also use a script to load your mods, but I prefer the GUI).
Other tools you may need are the standard Nvidia (DDS) Pluggins or 3D modeling plugins, depends how far you want to go.
Once you have the basics, this thread can be good too, yet it is written in parts assuming that you know what your doing:
http://www.twcenter.net/forums/showthread.php?t=238847
Hope this helps to start you up, don't hesitate to search the older pages of the forums some things are buried a bit.