CNAMEs, masking domain and adding directoris to end

I have car dealers websites as clients. They control their own domains and have websites hosted with some of the larger automotive dealer web hosts. I want the delaers to create a subdomain to hang off their mainsite urls. They will add these subdomain and point their CNAME to my specific WordPress multisite subdomain. We will then serve up content for pages we will host on WP Multisite. Or we will route it once pointed to us … depending on the best method, or combination thereof.

In essence, I want to serve up content off of my site as if it is on their site. But, I want to add to the end of the subdomain … directory structure from the content side of things tagged on the end as well.

Any thoughs as to how to accomplish this is appreciated.

It will look like this.

service.AcmeDealer.com >>>> displays and points to content housed on my wordpress multisite AcmeDealer.MainMultisite.com
accessories.AcmeDealer.com >>>> displays and points to content housed on my wordpress multisite AcmeDealer.MainMultisite.com
models.AcmeDealer.com >>>> displays and points to content housed on my wordpress multisite AcmeDealer.MainMultisite.com

So my questions are this:
1.) How can I accomplish this most effectivley? I was told by someone that mod_rewrite script might be needed to add the directory strucure to the end of the url.

We control the VPS the content site is hosted on and are running Linux.

Here is a structure:

MainMultisite.com
|
|
— AcmeDealer.MainMultisite.com
| |
| |
| |__ /service. (what needs to read in url: service.AcmeDealer.com/)
| | |_/tires (what needs to read in url: service.AcmeDealer.com/tires)
| | |_/oil change (what needs to read in url: service.AcmeDealer.com/oil_change)
| |
| |__ /accessories. (what needs to read in url: accessories.AcmeDealer.com)
| | |__ /clear coat (what needs to read in url: accessories.AcmeDealer.com/clearcoat)
| | |__ /matts (what needs to read in url: accessories.AcmeDealer.com/matts)
| | |__ etc.
| |
| |__ models. (what needs to read in url: models.AcmeDealer.com)
| |__ /Camry (what needs to read in url: models.AcmeDealer.com/Camry)
| |__ /4 Runner (what needs to read in url: models.AcmeDealer.com/4Runner)
| |__ etc.
|
|
|_JohnSmithDealer.MainMultisite.com
| |
| |
| |__ service. (what needs to read in url: service.JohnSmithDealer.com/)
| | |_/tires (what needs to read in url: service.JohnSmithDealer.com/tires)
| | |_/oil change (what needs to read in url: service.JohnSmithDealer.com/oil_change)
| |
| |__ accessories. (what needs to read in url: accessories.JohnSmithDealer.com)
| | |__ /clear coat (what needs to read in url: accessories.JohnSmithDealer.com/clearcoat)
| | |__ /matts (what needs to read in url: accessories.JohnSmithDealer.com/matts)
| |
| |__ models.
| |__ /F-150 (what needs to read in url: models.AcmeDealer.com/F-150)
| |__ /Taurus (what needs to read in url: models.AcmeDealer.com/Taurus)
| |__ etc.
|
|