to answer your three questions......yes, yes and yes
in theory...
in practice shrinking a partition often shrinks it from the "wrong end" so you end up with unused space at the top end of the drive, not the bottom.....meaning you can't expand into it
personally I prefer to use a dedicated Linux tool called GPartEd, which is far more flexible
There are a couple of specialist distros which have this
GPartEd Live
GParted -- Live CD/USB/PXE/HD PartEd magic
start
You tend to find that some PCs will only boot one or the other.
A tip is when they ask for the graphics type, try the VESA option
And yes there is a risk. Make sure your partitions have been scanned with chkdsk before starting, that you're free of virii, and get rid of any unwanted temp files and empty the recovery bin.