How far should I go with paint prep?

[Jim70Chevy]

Hi all. First, let me say how amazing this board is and how it (and Youtube) have been the things that even allowed me to have the courage to try this entire build. Thank you!

I am at a crossroads in my build (in my signature). I have finally stripped off the spray can primer from the whole truck. I have been addressing bodywork as I go and even starting spraying a 2 part epoxy sealer. I am now at a point where I am planning to go around panel by panel and make each as good as I can get. I then plan on taking it to a local paint shop to have a good (but not show quality) white or silver paint job done inside and out.

The question is how far should I go with prep before taking it to be painted? I am NOT a body guy but I am learning as I go. Should I finish as far as I can and then spray an epoxy sealer on it all or leave that to the professionals?

Also any tips I should know when approaching local paint shops to get it painted?

Thanks again everyone for your help.