You have a situation. You want to learn and figure this is an easy project. The homeowner probably smells the new and figures it is as simple as removing the wood and replacing with block.
The truth is that this could go horribly wrong and become a real problem. Done improperly the driveway edge will move and you'll have some ticked off clients. Cobble is expensive, but stepping the wall over several vertical feet will add up too. I agree a wall is not needed. Concrete a curb and be done. Let me ask you, are you planning on cutting the driveway out to lay your base in front of the wall or are you planning to place the wall back and fill in with patch. I'm fairly certain the owner is not expecting either and you can't just slap it up against the driveway.