Here is who I bought my secret audio from.
Good people but there ar eothers as well
http://www.customautosounds.com/classic/secret.html
You can mount the face plate under the seast in a glove box just about any place. It is small so I mounted it where I could see it.
If you use a CD player make sure you use rubber mounts and dont mount to close to a woofer. Mine if I turn it way up it skips with a CD no problems with the MP3