You would want at least one free partition of 2-3GB or more for Linux. Linux can read and write to FAT32 just fine so any files on those drives could be shared. Unless it has changed, Red Hat does not support reading NTFS on the default install. Linux installs also prefer an available swap partition (1/2, equal or double your RAM as needed). If you have a spare partions(s) you can use for Linux you are good.
If, after saving anything needed, you delete the partition(s) you want to use for Linux the Red Hat install should be able to guide you through the rest. Read the docs to be sure what you are doing.
You would have the choice of using your current bootloader (which you may prefer) or the Linux bootloader. If you install Lilo (the Linux bootloader) to the Linux root (/) partition rather than the MBR, and create a bootdisk, you would be able to boot Linux from the floppy until you added it to your Windows bootloader.