Great post, look forward to reading more.

you need to download the mesh first in order for recolored items (made from that mesh) to work.

i can't explain how exactly to make one, but the way I get them into the game is from sim 2 websites (not EA, but others devoted to sim items). I like http://www.thesimsresource.com the best.

there are THOUSANDS of items there, building, fashion, objects, hair, pets, etc. You can download some for free, but it's pretty cheap to join and you get a "basket" so you can download all the items you choose at once. Sometimes items will say "mesh file needed" but there is a link right there so you can download the mesh, too. (it says 'download the mesh at TSR')

There are directions on the site on how to download and open the files into your game. Watch for expansion packs needed on certain items. If you dont have the expansion pack mentioned, the item will not show up.

Good luck. I love adding items to my game and have tons of designs.
References :
A simaholic.

Now, to install, it doesn't quite go like the other answerer said. The files will likely be zipped, you can install them pretty easily without worry with Sims 2 File Maid or the Robo File Maid (links below). If you don't mind uncompressing them yourself, you can put them in your My Documents/EA GAmes/Sims 2/Downloads folder (if you don't have one, make one there.) As I said, object files can further be organized into sub folders (I make one for each site I use). Skin files can be organized like that too, if you have Nightlife or later.
References :
http://mattwork.potsdam.edu/projects/SimFileMaid/index2.html
http://www.modthesims2.com/showthread.php?t=119585

I REALLY hope this helps!
Andrea –Sims 2 Expert–
References :