You don't have to take off the chain nor worry about chainline. Move the wheel forward in the fork ends, and have the chain fall off your chainring. There should be enough slack to now remove the wheel. After you fix your flat, basically just do the same thing in reverse. Getting the chain tensioned right is really easy if you "walk" the axle. Tighten one nut, then move the next nut farther back in the fork end to tension the chain. Now loosen the first nut and center the wheel.

Of course the easiest way is to just patch the tube and not remove the wheel at all.

Good luck!