I know there are a lot of people out there who wish to get started with development for the n900. I see they become frustrated by the wealth/lack of information to help get them started. The forums are a good place but can be intimidating. Also, the documentation provided under the development section is excellent but not always easy for another user to follow.
I have written a simple guide on installing maemo SDK on ubuntu 9.10 with step by step instructions. You can find the guide here http://www.binaryworks.co.uk/?p=34#more-34. As I continue learning how to develop and pacakage applications I will write some more guides, to help people.
I hope this is of use to someone and I'm sure they're loads more out there but good luck to those starting out just like me!
No. But feel free to download virtualbox, vmware, or a similar virtualization software and use that to run linux from your Windows OS (there are downloadable pre-fab sdk images available too for just this purpose!)