XRAY - Model racing cars

Is this all I need to upgrade an m18 to the Hex Wheel Nut System?

XRAY Composite Drive Shaft
http://www.amainhobbies.com/product_inf ... haft-Set-2

AND, what are the correct specs and resources to use for tires? I understand the front is 14mm and the rear is 17mm.

No, what you will need are:
2 packages of these http://www.amainhobbies.com/product_inf ... Adaptor--2
or these
http://www.amainhobbies.com/product_inf ... -Adapter-2

and

2 packages of these http://www.amainhobbies.com/product_inf ... heel-Nut-2

I can't help you with tires, as I just run the mounted foam tires.

Got it. That's what I thought. AmainHobbies couldn't give me a definitive answer.

You don't really need new driveshafts. You can use your old ones but you will have to sand them a little to fit into the new hex hubs.