depends what you want to do, n how much the car is worth to you, I know this new engine comes with warrenty but you dont know the history. a rebuild would probably cost you £300 but you would know that every part you had replaced was good.
n would be a good experiance for you, I did a head rebuild n timing chain on my corsa a few weeks back n its good to start a engine up for the first time n say I did that.