Q1: Do a full backup before. Use an external HD and free software like
Carbon Copy Cloner or
SuperDuper (free for full backup) to do it. Be aware that the next version of Mac OS X will be out in October, you may want to delay your Mac OS X 10.4 purchase?
The update process is pretty much straightforward, disconnect all your external peripherals (except mouse & keyboard), put the 10.4 DVD into your Mac, restart your Mac and keep the C key pressed to boot on the 10.4 DVD and follow the instructions.
Q2:
Transmit is my favorite but others products such as
Yummy FTP,
Interarchy, Fetch are also available, this list is not exhaustive.
Cyberduck is a free alternative.
You can find software by using either
www.macupdate.com or
www.versiontracker.comQ3: PhotoMecanic is available for both Macs & PCs.
HTH