What should I do at the Shortstop position?

Both Drew and Tulo have proven to be great player. You say you are in first place, so just wait the two of them out. At least one of them will come out of there slumps soon, they are both too good not too. As far as your RP goes, when Soria gets healthy you will be set. I wouldn't doubt you winning your league with the guys you have now. GL