external screen for photo-editing

I mostly edit my photos for web-publication. Currently, I'm thinking of buying an external screen because the built-in LCD of the Macbook Pro is not really suitable for good post work. With the Dell U2711, I can get a resolution of 2560x1600, this sound great, but I still have a few questions about this.

First of all, I'm not sure which cables I need? I have a Macbook Pro 17-inch v4.1 (from 2008): do I need a dual-link DVI cable? Something else?

Secondly, I'm not sure if I'll be able to close the Macbook and work with an external keyboard? And can I work in Dual Mode (both screens active and working on an 'extended desktop') ?

Last but not least, I wonder if this high resolution can also be a disadvantage? Sure, the extra real estate is tempting and it will increase productivity when working in Photoshop. But, if I'm going to review the photo in the final web-resolution (only 800px high), I wonder if it will be too small to notice any remaining mistakes. I realize this will probably sound weird to some people?

Thanks in advance for your help guys,
-Kris

1.the dell monitor should include a dvi cable. this is going to be the only cable your going to need.

2.space bar will wake your macbook. you can also run both screens at the same time.

3.as for the third question. i think you would be ok. but the might be something might just have to try to see if its ok with you.

Thanks for the reply.

The screens are given a basic calibration by default in the factory. Do you think I could still benefit extra from using the (low-end) Spyder3Express calibration device (or another one)?

i would think it would be worth it. really depends on how different the colors are when you get the second monitor