If you get alot of that laquer primer off your heading in the right direction
Any primer with hardner will be 1000x's better than laquer. Block and sand as you would with the old stuff. It just won't shrink back and fail like the Laquer.
Depends on what grit your body work is done in now. 80/180?
Just remember that you'll see every flaw in black!
You'd be fine with 600-800G on your final prep before going directly to your (basecoat) or single stage. Base clear would be my suggestion but to each thier own. You can clear right over some single stages and have a good durable finish that looks miles deep. Check with the paint manufacture to see how they recomend doing that. I've done it several time before with great results.