8800GTS and It's Size

Okay, even though I can barely afford it I was thinking about buying an 8800GTS 640MB... but since I don't really know much on computers I was wondering if someone could please help me, k?
So my computer is 42cm in length, and I saw on some website that the GTS is approx. 23cm. So my questions are:
1. Do you think the 8800 will fit okay inside my computer?
2. Do you think I will need an extra cooling system for the GFX card since I'm also gonna upgrade to 2GB RAM. (Does RAM make the computer more hot? lolol)
3. If I need an extra fan for the cooling then do you think that will fit in my computer too?
4. Would you recommend a better GFX card?
5. How much do you think a computer shop would charge to fit it in? For example PC World. (Apparently they're shit but meh.)
Oh ye also what power supply should I get? 500W? o_o
So my computer is 42cm in length, and I saw on some website that the GTS is approx. 23cm. So my questions are:
1. Do you think the 8800 will fit okay inside my computer?
2. Do you think I will need an extra cooling system for the GFX card since I'm also gonna upgrade to 2GB RAM. (Does RAM make the computer more hot? lolol)
3. If I need an extra fan for the cooling then do you think that will fit in my computer too?

4. Would you recommend a better GFX card?
5. How much do you think a computer shop would charge to fit it in? For example PC World. (Apparently they're shit but meh.)
Oh ye also what power supply should I get? 500W? o_o