Hey, well no not really in your case. If you can make a new tape (or verify yours still works) before you install you can save yourself a lot of grief. I actually made three copies before attempting it myself. You may want to run a cleaning tape through the drive too...mine was filthy.
IIRC, the install script won't go stomp on AmigaDOS partitions, but be careful during the install process :-)
As an aside, there has been some behind the scenes activity on my end re: AMIX. I have the contents of the mmhart.com site (manuals, etc), as well as the X11R5 patches for AMIX, and a variety of other things. Another individual has provided scripts to create install tapes from Linux (verified working). He is going to help me revamp the site a little bit, and for my part I plan to get the files uploaded by this weekend.