I moved a few months ago, and I haven't had a need for the CS disk until today. I want to do some retextures, but now I can't find the disk. I still have my Morrowind disk, but the CS disk is probably still packed somewhere.

Is there any way to access resources from the MW disk, or am I pretty much screwed without the CS disk?

You can unpack the bsa files of your Morrowind installation, that will give you most of the original textures and models. I'd make a backup first, especially if you used texture replacers, as those may be overwritten in the process. Or make a new installation specifically for creating mods, and unpack the bsas there.

How do I unpack the bsa files?

Or just copy the BSAs out, unpack them, and copy the files back (not overwriting files during copy).
The BSAs contain everything you need, and a few files that are not on the CS disc.

To unpack BSAs, use BSAPack:
http://www.uesp.net/wiki/Tes3Mod:BSAPack

A few other options: http://www.uesp.net/wiki/Tes3Mod:BSA_Browser, and http://www.tesnexus.com/downloads/file.php?id=12189.

or you can ask someone with CS disc to make an iso for you

actually i have a backup copy of all mine TES3 CDs - i once lost my CS cd too and by some miracle found it after 1,5 years later so i prefer to have a copy now
mine CS cd is about 577mb in *.nrg format

if you'll need it sometime, email me nina.el (at) google.com so we can discuss how you can get your hands on that file. i don't think google will let me upload it as mail attachment (tryed with smaller files) but there must be a way

Bad, bad idea.
Making a back up disc yourself is within the terms of the EULA.
Sending it to anyone else becomes copyright infringement, piracy, and what not. Not good to discuss here, despite the fact your motives are good.