I need to take the old one off and replace it with another.

Are there any traps for the novice?

Do I need special tools?

Do I need a torque wrench to tighten the new one?

um there is a little tinware to take off then when you have the big nut off use a nice puller to remove it then id use a little lube on the new one the a nice bit of timber to tap it in oh and put the nut back on just do it up nice and tight not to hard!

How tight is "nice and tight"?

Is the engine in or out of the car? If out you will either need a fly wheel lock or a bit of anlge iron to stop the motor from turning.
If you do not have a calibrated arm, I would suggest you use a torque wrench to do up the nut.

Thanks PT3

It's out of the car, and I think I have a flywheel lock lying around somewhere.

Found it - 4.5 m/kg or 33 ft/lb