Sorry for my slow reply, I normally pounce on threads like this. Welcome to the forums by the way.
I always use Notepad to edit xml files. You can find the references to the structures and ships in your Supremacy\Resources\Data folder - look for a file called TechObjectsDatabase.xml. Alternatively if you want to change the descriptions of the ships or structures, load up the file called TextDatabase.xml.
Editing the file can be tricky because you've got to ensure you maintain the layout and code within the file. Changing things around may prevent the game from working, so before you make any edits BACKUP THE FILE(S) YOU WANT TO CHANGE FIRST.
The text entries for each structure continues without any breaks, so it can be hard to identify individual structures in the files. The easiest way to find stuff is to use the search function, which is Ctrl+F. Enter the name of a structure, for instance starfleet_intelligence to find the code entry for the building.
I would also recommend that when you start making changes, you start off changing small things, such as the existing build costs of a structure. Here's an example of the code for Starfleet Intelligence:
Code:
<Building Key="FED_STARFLEET_INTELLIGENCE">
<TechRequirements>
<BioTech>3</BioTech>
<Energy>3</Energy>
<Computers>3</Computers>
<Propulsion>3</Propulsion>
<Construction>3</Construction>
<Weapons>3</Weapons>
</TechRequirements>
<BuildCost>3950</BuildCost>
<IsUniversallyAvailable>false</IsUniversallyAvailable>
<EnergyCost>60</EnergyCost>
<Restrictions>
<Restriction>OnePerSystem</Restriction>
<Restriction>HomeSystem</Restriction>
<Restriction>OnePerEmpire</Restriction>
</Restrictions>
<Bonuses>
<Bonus Type="PercentInternalSecurity" Amount="15" />
</Bonuses>
</Building>
As long as you read the entire entry before you start reading it, you should be able to identify what the different bits of code mean. For instance, if you want to change the build cost of the structure, just change the number that appears within the Build Cost tags.
One thing you should be aware of is that if you make changes to the files, the games auto-updater will attempt to undo any changes you make; it incorrectly identifies mods as "outdated" files, so the next time you load up the game you will be told that an update is available. Do not allow the update to continue or your modifications will be lost. You can turn off the auto-update in the game options, but this will also stop you from checking for legitimate updates.
If you decide to try multiplayer, you should also be aware that the game won't work correctly if you have different files to those you play against. Make sure you send a copy of your own files to your friends or revert to the original files before you start a multiplayer session.
As .Iceman said the May update stopped the editor working which is why it doesn't currently have one. We're hping the next update will bring it back. If it does, you won't need to bother with text editors. Until then though, you'll have to continue editing it manually.
Have fun.
_________________"Anyone without a sense of humour is truly at the mercy of the rest of us."