How can I save my carefully constructed printer presets before I have to re-install my printer?
Your custom presets are located in

${HOME}/Library/Preferences/com.apple.print.custompresets.plists


Now, it is possible that it may have the printer name "embedded" in the filename.  For instance I have an HP LaserJet that I name "HP Color LaserJet" so for me, my plist has the following name:

com.apple.print.custompresets.forprinter.HP_Color_LaserJet.plist


If you want to see what's in the settings file, just issue the command

defaults read com.apple.print.custompresets.forprinter.HP_Color_LaserJet.plist