Paint and Body guys.

[Hopper111]

I'm kinda at a loss for what I should do on my El Camino as far as paint/body goes. I know what color and paint scheme I want, I am just in the dark about if I should try to take the body down to bare metal or just block it up and paint it.
The car is in gray primer right now and I can see a green layer in the engine bay area, but I have no idea as to how many layers of paint (if any) are under that green layer. Now, a paint friend of mine advised that I clean the gray primer really well, sand it, and start my paintjob from there because he said that if i try to take the whole car to bare metal and start all over again there is a ton of work and a lot more money involved.

Do you guys have any advise on this? Are there any pros and cons to blocking and paint vs. a fresh new bare metal paintjob?

The car is grey primer now, I wanted to shoot a layer of black over the top of it, and then start into a silver or possibly dark brown color coat and a nice, smooth glossy finish.