So I've trying to mod the sims medieval and I was told to use sp3e. It works to open the packages but the editing tools are all greyed out. I can't edit using the text editor or the hex editor. I tried moving the file I'm editing, as well as the sp3e program to folders that weren't write restricted, but it doesn't seem to do anything.

What am I doing wrong? How do I access the edit options?

Nevermind, I figured out the problem. I had to link an external editor. That said, once I loaded up the editor (notepad++) it just loaded a bunch of garbldygook. Is this the right editor I should be using? I was expecting to see some programming language with lines of code.

Am I meant to edit this using hex language? Equally as confusing.

Or am I meant to take a course specifically in sims coding to understand what the nonsense in the editor means?

It depends on what you are trying to edit, as S3PE has access to literally all of it. Every resource inside of a package can be quite different. Some are textures, meshes, etc that are of no value opening as a block of raw text. S3PE is incredibly powerful and can modify a fair amount itself, as well as be the middle ground to export files out for editing.
The game files aren't just raw code after all, there's a few dozen different file types all working together to make a whole.

Understanding how script modding would indeed help you understand why you're in the game files to begin with, and what in there is of value to you or if what you want to achieve even requires scripts.
The TS3 pure script tutorials should more or less cover the same process, give or take what TSM shares or varies with, of exporting the game scripts and referencing them in a mod. The language used in this context is C#.

That's quite an advanced place to begin, though. A lot of valuable things are defined in the _XML resources too, which is a little more user-readable. Changes to these are referred to as 'tuning' mods, as you're limited to adjusting tunable values. These can be edited in the text editor, as an xml is already a type of text file.

Finding TS3 equivalents of what you want to do will help point you in the direction of the resources that will be relevant and what editing them involves.

Thanks for your help. The problem I had was a missing wrapper. I can now edit the file. The issue now is that when I save the _xml it doesn't update the package. I've modded the file 3 or so times now to no avail. What am I doing wrong here?

The text editor technically opens a temp file that should be applied when you save and close it (a popup should appear asking to save changes).
If it's losing that connection and not saving, you can also right click on the _XML and Export to File. Then you can save it somewhere on your PC to edit normally. When the changes have been made, right click on the original again and select 'Replace', which will prompt you to overwrite it with the edited file.

You may also want to avoid overwriting the game files directly, in which case you would import the edited XML into a blank package and install that as a mod instead.

Thanks. I actually figured this out, but unfortunately it screwed up the game entirely. I was editing the buffs xml and tried saving it as a txt file, and a c++ file, but both times the result was that it removed all buffs. What file type am I supposed to save it as so that the game will recognize it when I replace it?

I finally figured it out. I needed a DTTB convertor for the file. Got the mod working. Huzzah!

The file should export as .xml, which is a type of text file that can already be edited in Notepad / Notepad++ / etc. There shouldn't be any need for converting file types in the future (a .txt can also be resaved as .xml without issue), but I'm glad you were able to find a workaround