Repainting my car, have few questions.

To all the pro painters out there I need all the help I could get. I am considering repainting my galant before mod which is less than a month away. I have plenty of hands ready to help and make this happen but I need some questions answered.

I was told that I do not need a primer since I'm shooting the same color and only to use sealer over body work area and sand down the clear completely down to the paint and shoot over that. Is that true??

Also a gallon of paint is enough to spray the whole car, is that a reduced gallon?? If so then I only need about a half a gallon of lets say 1:1 paint cuz that would make a gallon after reducing. Right??

I know not to rush things but I really wanna do this and trying not to go overboard with the spending.

Ant help and pointers is appreciated.