Topsoil mixed with play sand would do well. You don't want anything that holds a lot of humidity. Greeks only need about 30-50% humidity or they become susceptable to
upper respiratory infections. Make sure you add a couple of inches of substrate -- Greeks like to dig and bury themselves.
Not a lot is known about tort lifespans. We have only recently made significant advances in chelonian husbandry ... Since most torts are
capable of outliving thier keepers and records are not always kept it is hard to give a good estimated lifespan for most species. It is doubtful that we will be able to come up with a valid "average lifespan" for another 50 years or so. For now, the best answer I can give you is that how long your tort lives depends on the individual tortoise and how well you take care of it. Assuming all goes well, I would consider 50 years to be a low-end estimate.
You will have to gauge how much to feed him based on how much he eats in a sitting. The first time you feed him let him eat until he is full and remove the rest of the food. The next time you feed him give him that approximate amount. Torts get fat if they are allowed to free-feed but should be allowed to fill up in one sitting. Greeks should thrive off a diet of grasses and weeds supplemented by dark, leafy greens. Remember to feed high fiber -- low protein.
If he is healthy he will eat immediately but don't be surprised if he doesn't eat a lot at first. The stress of his new environment can cause him to lose his appetite for about a week or so.
