I have not made anything for San Andreas so I can't really help but I'm sure you could find an easy to use tool for download to put your textures into a txd file.
Here's one, but I've not tried it yet. Looks similar to the txd workshop I have for Vice city. Shouldn't be hard to use, plus I'm sure it will come with some instructions.
http://www.gta-downloads.com/database.php?act=file&id=3203
When it comes to making stuff for GTA I find it's best to do as much as you can on your own. Mostly because finding people who can do what you want to have done is hard. Plus it gives you a better feeling when the mod is done and you think, “Wow I did this all on my own”.