Good results, like many things, come from practicing. Remember what Scott says, never every try something new, for the first time, on your airplane.
I suggest, if you are concerned about this, to take a piece of "scrap" bang it up a little then perfect your techniques to straighten it. Don't use a hard faced hammer and hard faced back up tool as a dolly, that WILL stretch the metal. Try it.
Try a smooth face cutting board backed up with metal for mass, and a low crown body hammer. Do a trial piece that is flat and see how hard you can hit it before it stretches, cups. You may have to remove that rib to get full access. A seaming plier is a good start, but just to clamp smooth , don't bend.
If you use wood as a backer, use a fine, even grained hard wood like oak, cherry, hard maple, or ironwood. Make the working face smooth, not a sawn face. A soft wood will give more and more likely to have to hit it harder, not recommended.
Look here for inspiration. Kent is a true master.
Good luck!, I know you will get it.