Roof cracks

If it's lead and the body seam is in good condition, you can leave the lead in there.

If you have corrosion in the seam and need to remove the lead you have several options but none of them are really good for you and you will want a respirator, not just a dust mask.

You can wire wheel, sand or grind it out. If you use heat like a small torch to flow and scrape it out you will need to remove that part of your headliner and interior or you will catch the car on fire.

In an area like that I would probably use something like this.
(But like I said. I would really need to see what you find once you get it cleaned up.)

http://www.autobodytoolmart.com/usc-all-metal-premium-aluminum-filled-auto-body-filler-p-14787.aspx
[ame]http://uschem.com/products/docs/TDS_ALL-METAL.pdf[/ame]