Are there any guides for the G.E.C.K. available which use references to New Vegas instead? I'd like to learn how to use the G.E.C.K., but I'm not sure how to go about it with the tutorial from Fallout 3, which I don't own.

Well you can read the Fo3 one as like 99% of the geck is exactly the same. Just some of the actual people, places, and things are a little different. But the concept of using it is the same.

Here's a http://geck.gamesas.com/index.php/Category:Getting_Started#My_First_Vault_Tutorial_Series to what Gunmaster is talking about. You should find it useful.

If you'd rather have it in video form head on over to http://www.youtube.com/bethesdasoftworks.

Once I finish my current mod (im like 95% done after like 11 months of work. ) I was also considering making a video tutorial series for the NV geck. I would of course have to use it some first, but considering its mostly the same I would then make videos. Though I'm really not sure how that will play out. So if you wait like 3-4 months I may do that.

Can the GECK edit existing or create new perks?

I'm not sure about that, but it's possible. I haven't seen it under the script effects when searching stuff for recipes.

The answer is it can most definitly do both! You will find all the perks in the geck, and the tools needed to make your own if you want. Just be careful, there was a bug in Fo3 where if a mod added a perk, and the mod was disabled while the player had the perk, it would corrupt their save. Make sure people know to use the console to remove any added perks before removing your mod.

The section of the file you're looking for is Actor Data -> Perks.

You can either right click -> New or take an existing perk and change the ID to have the GECK make you a copy automatically that you can then change to your heart's content.

You can also edit everything about any existing perk, both levelup, follower and quest granted.

Oh, and PredatorX: Perks don't use scripts by and large, they include their own mini-script-like effects. Basically you can pick a defined effect (found under Actor Effects) or a defined numerical operation and what to operate on like "calculate my critical chance, multiply by 1.05" for 5% bonus crit chance.