[dogscoff]

Right now, i need to know what i need to add / modify in the txt files to use the ships.

OK, the neostandard isn't a set of new ships, it's a set of new images. It sounds pedantic, but there's a vital difference.

To answer your question, you don't necessarily need to add anything- just install the neo-expansion pack, then play a game using devnullmod or P&N or Proportions or something. You will soon see neostandard images.

If you still want to modify the text files, that's not a problem, you'd need to make a few additions to your vehiclesize.txt file.
There are plenty of modders and faqs 'round here that can tell you how that file works, but what values you add is entirely up to your imagination- it would be your mod after all. (That's the vital difference I mentioned earlier )

If possible, in a way that only the races that i want (the ones thta i have the ships pics)use it.

In SE4 gold, every entry in vehiclesize.txt can have a primary and a secondary image attached to it.

I'll clarify thius with an example: In the standard game, the baseship will use baseship.bmp if it is available, and if it isn't available the baseship uses the starbase image. What this boils down to is that if a particular image is unavailable for a particular race - it doesn't matter at all.

One of the ideas is to have only one race with that capability and trying to fight against / for that one.

As I said in the previous paragraph, missing image(s) do not require that a particular race go without certain ship sizes.

Having certain hulls only available to certain races is a possibility though. It's not simple, but it is possibile. Take a look at the data files for Pirates and Nomads, (look at the tech requirememtns in vehiclesize.txt) and see how certain hulls are only available to nomad races.

If none of the above makes any sense to you and you are still worried, my advice would be to install the neo-expansion pack and forget about it. You don't need to do anything more to benefit from the extra images supplied, and having them there will not create any kind of incompatibility or imbalance. They'll just sit there waiting to be used by a mod like the ones mentioned above.