That's not how that works. You'd have to change your Y to an X in all your cells. Anyway, that foreign DNA is why organ rejection exists, and why transplant recipients need to be on drugs cocktails about as powerful as people with AIDS have to take. It isn't really just about the blood type; but once the cells start repairing themselves, I would imagine they'd be overwritten with your DNA.

Anyway, this therapy is still in the early stages, but they've already started to use it for to correct one or two types of genuine birth defect (that is, badly-coded DNA).