I don't have any great DIY ideas, but if you feel like spending a few bucks, a body shop should be able to pull the dent out for you pretty easily using a stud welder, sometimes called a "spitznagel". A nail-like stud is welded to the dent, then a slide hammer is used to grab the stud and pull it out. When done, the studs are ground off.
George Davis
'69 280 SL Euro manual