No, they're not the same kind of tissue, but they can be interchanged, to a degree. For coronary artery bypass, the saphenous vein (a leg vein) is often used.

Arteries have thicker walls than veins, and a thicker layer of muscle inside them. Except for the pulmonary artery, arteries lack valves. Veins are thinner-walled, with a thinner muscle layer. They also have valves. These valves prevent blood from pooling and flowing backward (gravity and all that), and, because venous pressure is lower than arterial pressure, the valves "help" pump deoxygenated blood back to the heart.

Edited to add that veins and arteries can also purposefully be connected together to create an arteriovenous fistula, for dialysis access. Arteiovenous fistulas can also occur naturally, as congenital defects.

So the answer to both of these is yes but no but kind of.

Your veins have valves in them to prevent blood from pooling backwards along your limbs and trunk due to gravity. Veins aren't driven by the beating of your heart, after all, and the blood is trying to go up against gravity; without the valves, you'd be in kind of a really bad spot.

You can technically use a vein graft to replace a stretch of artery in a pinch -- the valves won't hurt you too much -- but replacing a stretch of vein with an artery would be a majorly bad move.