Hardtop Question
 

I have an 04 911 Turbo Cab. It didn't come with a hardtop, but I've seen ads for used ones that fit the 996 from 99-04 model years. I'm considering buying one but had some questions:

1. Are all OEM hardtops interchangeable for the 996 models built between the stated years (99-04) ie. the hardtop will fit a C2 or Turbo, it wouldn't matter or are there special ones for the Turbo?
2. What steps are required to place one of these hardtops on and is there hardware necessary to do this? If anyone has a step by step thing with pics, that would be greatly appreciated (or if you know of any links that show this).
3. My coworker has one, but he says it just takes up space and he's only had his on twice, once when he bought the car and the second when he was moving out of state. Is it not worth having it? Opinions welcomed here.

Thanks