Im using this tutorial:
http://le-plat-du-jour.livejournal....703.html#cutid1

Which in incredibly easy to follow. I got all the way up to the point where it says "add the mesh" about a third of the way down, then I run into a brick wall.

Im trying to default the sims 2 store spooky vampiress/Bride of the Night/Pumpkin head dress on top of the nightlife contessa gowns. (side question, how do I unlock the hidden red one to default that too? It dosnt show up in bodyshop)

So I need to add the mesh from the item that I want to make a default, but the store dress comes in self contained files, and dosnt have a mesh only package, so, how do I do this? Do I just change the group/instance numbers inside the Store dress files? Or...?

EDIT: For unlocking the red one, would Morgues tutorial work?
http://www.modthesims.info/showthread.php?t=38392
Im assuming it will show up in bodyshop as custom, so do I extract that and follow the tutorial like normal and it will work? Or no?

The store files do have mesh packages... but they're not in the same place as all the regular mesh packages that come on the game disks. (Trust me... they're there somewhere. I've used the meshes from the Sims Store in my projects.) Try looking in C:\Program Files\EA GAMES\The Sims 2 Store\TSData\Res\3D (or something similar to that... what you're looking for are the GMDC files, which are the actual meshes).

As for making defaults, that's outside my area of expertise, so hopefully someone else can help you out with that.

EDIT: I just looked at the first tutorial you posted, and it seems to be a bit out of date. There are easier ways to make meshes than by gathering up all the mesh parts by hand. What I would suggest is going through the Unimesh tutorials on this site (you can build a mesh package really easily with the mesh extracting tool in SimPE... it gathers all the parts for you automatically) and then replacing the GMDC with the GMDC for your new dress. Once you've got a working custom dress, then you can use one of the tutorials to help you turn it into a default.

Thanks for the reply fakepeeps, it really cleared up alot of the confusion I had. Im basically finished, each dress it replaced and fine, but im having one small issue which im not satisfied with. The frill edge on each dress is the same color, red. Only the black dress is supposed to have red. The purple is supposed to have yellow, and the red has black. Any idea why its doing this? The texture files in the file are just fine, all frill are the right color. But on a sim they are not.

It looks like the frill will be an alpha piece on the mesh, which means it has a separate texture file. If you're making the purple dress, you need to find the texture file with the yellow ruffle and attach it to just the alpha part of the mesh. Right now, the alpha piece is probably defaulting to the red ruffle texture. You need to point SimPE in the right direction. (Sometimes EAxis will combine the textures for alpha parts into one texture image, so if you want to mix and match you have to attach different textures to different mesh parts.)

In SimPE, you should have two TXTR and two TXMT files. If you don't, then you'll need to add them, because it looks like your mesh has two parts (the body of the dress and the alpha ruffle). Instructions for adding alpha parts to your recolour package can be found here. (Though I'm not sure if you'll even need to do this... I don't think your ruffle would display like this if the recolour package wasn't already set up for it.)