A little advice if you are asking:

RTS runner has the right Idea here. I have been a bodyman most of my life and here it what I would do:

Remove all of the old seam sealer

Clean up any rust in the area

Apply a 2K seam sealer. I prefer the 3M Impact Resistant Structural Adhesive IRSA for 3 reasons.

1. It is epoxy based and will work as good or better as epoxy primer

2. It has a long work time to tool it and let it flow out.

3. It changes color when curing so you know the stuff is ready to go.

Hope this helps. By the way, IRSA is a structural adhesive that works great as a seam sealer too.