1. I use Gnome, but KDE is just as good. I personally don't prefer one over the other.
2. The partitioning software on disk will work fine. Just make sure you know a bit about the partitioning formats to use for linux and windows as some provide more benefits over others. Fedora partition will probs use ext3. Decide how much space you want for each partition. Windows (NTFS/FAT), Linux(EXT3), Linux Swap Space. You could even use a FAT32 partition for sharing data between Windows and Linux.
3. Pretty much any linux distro will run faster than windows. I wouldn't be too concerned about this.
4. Here's a good link to read if you want to know more...
http://www.thpc.info/dual/win7/dualboot_win7+fedora11_grub_on_win7.html