A flat universe, does WMAP support this?

I'm not a big fan of the big bang theory myself (not that I do or don't believe in it). However, I've heard that the WMAP data shows support of the big bang and also provides that the universe is flat with the curviture like in a saddle or sphere. Is this flat universe three demensional? By that, I mean does the universe go straight in every direction (but not with a postive curvature like a sphere), or is it actually like a sheet of paper with the paper being the universe and above and below there is nothing and therefore being 2 dimension on a small scale? Is there any evidence that the observable universe is larger than the real universe, in the sense that galaxies can reappear and become distorted tricking us into thinking the universe is larger than it is? I know there is gravitational lensing around some galactic clusters, but does this really factor in the hall of mirrors theory?