Haven't done it but the answer to your first question appears to be addressed well at:
On your second question:
You'd unmount the NTFS filesystem if still mounted.
Use fdisk or parted to change the partition type from NTFS to Linux LVM
Run pvcreate on the partition to make it a Physical Volume (PV) ready for LVM
Use vgextend to add the new PV to your existing volume group (VG).
Use lvextend to add the new space in the VG to the logical volume (LV)
Use resize2fs to make the ext* filesystem use the space that was added to the LV. (Assuming this is an ext2 or ext3 filesystem).
In Linux there are manual pages for most commands. You can run the following to get more details: