How do I edit a sim in the neighborhood with Create A Sim? I want to use cheats and I don't like to use mods or anything that has to do with downloading to solve a problem. I really want to give Cassandra Goth another skin color and I don't know how to do that.

Except for hair and makeup (the mirror) and plastic surgery (Uni - Show Business career reward), you cannot edit a neighborhood Sim without using some pretty substantial mods or external programs like SimPE.

I think there was a specific skin-color changing mod, but it took me quite a while to find. This was several years ago, though, so maybe there is an easier solution now.

To change a Sim's skin tone you most definitely need SimPE to do it. Plus, you need to know the code of the new skin. If you don't know it, there must be at least one Sim in your game who has this skin tone, so you can open his/her file --in SimPE, I repeat-- to copy it from there.

Check the section How do I change my sims' skintone? at Sims2Wiki.

If you still find the instructions confusing, try Verso's short tutorial here:
http://www.lothere.com/verso/page/16

you can always use default replacement skins unless you really wanna be bothered with the hassle in sims Pe.

what mod do i need? and will it mess up my computer?

Christianlov made a skin changer, but only for skins that were built into it. (Although there was a tutorial on how to add a skintone.) I think it's in the sims 2 graveyard now, though.

For a default replacement you get a skin set that is labeled as a default replacement and put it in your downloads. From that point on any sim with a Maxis skin will use that custom skin set instead. So if the custom set has everybody with the lightest skin being yellow, everybody who is darker being green, everybody who is still darker being blue, and the darkest being purple, you will start seeing rainbow colored sims.

To remove it you take it out of your downloads and everybody goes back to normal.

As to exactly which one you need; there are a lot of them out there. Find the one you like the best, and make sure it is listed as a default replacement. It also helps if it is geneticised.

Ghost sdoj, thank you for the helpful comment. But where do I find default replacements similar to the maxis skintones? A while ago I put a skintone set from paysites.mustbedestroyed.org onto my computer but they weren't default replacements. They are just like the ones from maxis but they are more detailed. These skintones were dark, medium-dark, medium-light, and light just like the originals. I just need something to change her color. P.S. I don't trust paysites.mustbedestroyed.org because with some things, you don't know if it has a mesh or not.

Not really a matter of trust, the booty is just a dump for payfiles. However the original site packed them up is how you get them. If you really want to know what you're downloading, you need to have the paysite open in one window or tab, and their booty page open on the next.

I've been using Lyran's default replacements for years. They are basically Maxis's skins with some extra facial detailing and nipples for the females.

I thought that you could enter boolprop, shift-click on the mirror and get an option to change appearance that would allow you to change more that just hair and accessories. I haven't actually gotten around to trying it myself, but I read that somewhere. Please someone tell me if I'm wrong, I don't want to try it later and crash my game or something!