Trying to set up custom carsets, help appreciated

Hello,

I just located this program a few days ago and it seems like it'll be perfect for me to run casual season simulations. I've been trying to figure out how to get stuff modded and have figured out some basics (changing performance data in TeamEditor, changing track order with Track Installer, etc), but I've been failing at finding out how to change the cars in the game.

Most of the old tutorials I find links to are either dead links or require a program that refuses to work with my version of gp4 (gp4master is the program in question). The only other thing I see people use is CSM, but I can't figure out how to make the program work or if there's another way to do it. I tried to load a 2013 mod into it but it failed to work, I think it couldn't find the car models or something :/

Specifically what I want to do is be able to create custom carsets (i think that's the right term), so that I can insert the teams and drivers I want into the seasons as they change with my simulations. If anyone has any direction or a more recent tutorial, I would appreciate it.

Let me know if you need more specs