Painting the Dart

wondering if I needed to remove all of the other paint before respraying or if that’s already a good base?

You need to prep the surface appropriately. You don't have to strip it to bare metal as long as there's no rust or surface issues. Lots of folks do a scuff and shoot for a daily driver paint job. I'd recommend a good book on auto body and paint. Paint is only as good as what is under it.

Automotive Bodywork & Rust Repair

How to Paint Your Car on a Budget