I agree, use the bottom-side D0. I have soldered before, but never points as tiny as the D0, and not for some time. I did a header pin install a couple weeks ago, and nearly passed out when I cracked the Box open and saw the actual D0 on the top side. But the one on the bottom was trivial, took 3 seconds to get a good solder on it.
Keep practicing, read up about PCB soldering, and get a fiber pen to clean the spot. It's well worth it. Also make sure you have some REALLY fine solder. I used .015 silver solder from Radio Smack (Part #64-035). And get some desoldering braid in case you have to back off. I splashed a little solder onto a trace while filling one of the header pin holes and might have been in trouble without the braid. Oh, and file down the tip of your iron to a needle point.
It's not hard, just takes patience and a steady hand. Take your time.