How to diag a faulty turbo?

1.how do you check the play in a turbo? wiggle the shaft up n down? or push it back n forth?

2.if the shaft had gone? will there just be play or will it cause the turbo to smoke?

3.if the turbo is leaking on the exhaust side of the unit, will the play in the shaft cause this?

4. what side of the turbo will be faultly if there is excessive oil in the charge pipes?