I recently bought an extra 300 60. My question is, do extras have dihedral, or are they strait? This one has dihedral, should I remove it when I put the wings toghether?

The wings on an Extra are straight. A small amount of dihedral won't affect much but the appearence will be a little strange.

The top of the wings are straight. The change in wing thickness root to tip give dihedral.

3-views that I've seen show that the wing is perfectly straight with no dihedral at all.

The particular airplane in the picture, an older 35% Carden, is mine. The wings are straight and the taper is equal both ways. There is no reason that the top surface could not be made flat and let the taper serve as dihedral but it is not necessary. It will fly hands off from horizon either upright or inverted.