Is there a modding guide?

Hello, after some thread searching I came up empty. Well, not completely, there is this thread, but it doesn't explain how to install the mods and check if they are working.

After some more investigation, I found that if you zip the files you altered and leave them with the right structure that they would have in the "assets" folder, then the xenonauts Mod installer tool can copy it to the "mods" folder. Sounds good, but the problem is that I've installed a mod, it has successfully copied to the mods folder, it's selected in the "Load Mod" drop down menu, yet i don't see the changes occuring in the game at all.

How do i check if the mod has loaded?

I haven't checked in a dog's age, but the mod launcher broke at some point. Most mods arouind here will simply overwrite the existing files. Taking Max's UFO analysis mod as an example, you install it into the Xenonauts\assets\ folder and load the game up as normal.

^Stinky beat me to it

This does mean that most mods are not compatible if they alter the same properties in the game.

For example if two mods both added a single new weapon you would be unable to install both mods.

You can do the work yourself of copying all the changes over to a single set of modded files if you find some you really like but that is still no guarantee.

But if i simply overwrite the game files, won't Steam automatically detect a game files integrity problem and try to re download the game?

Not unless you 'verify the integrity of the game cache' or the game has an update (and this depends on the update.).

Steam monitors certain files, most of the xml files are not on that list so they can be easily altered for testing and modding purposes.

Well, i backed up the game and replaced the original files with the modded files and it worked. I seem to have screwed up the AI though, since both aliens and civilians now run to the top left corner of the map and just sit there. Anyone has any idea what i might have changed that affects such thing?

The primary file that affects AI is aiprops.xml, if you're having problems, then try replacing that one.