A friend of mine has a 96 Impala SS. His opti went out and I told him I would help him replace it. How hard is it to do and do you need any special tools?

 

You'll likely need a 3 claw puller to remove the harmonic balancer. Other than that, regular tools are needed. You'll need new water pump gaskets too. It's not difficult, shouldn't take more than 6 hrs for your very first time.