Caulk Crack

I'd just use a decent quality seam sealer and something small to apply it in the crack. Then touch it up. It's not a repair that's going to last forever but a last forever repair might not be worth it for you.

I know there's a right way and a wrong way to do things but I certainly wouldn't spend a dozen hours and the $1k+ to work all that sealer out of there, reseal, prep it and pay someone to paint it. Especially on a 4 door.