Upgrade from 5.1.6 to 9

[nate at int-res.com]

Hello,
Has any body ever upgraded from 5.x to 9? I think it will probably be 
a colossal amount of work, but I have no idea where to start. Can 
someone please give me a clue as to where to begin? What sort of 
inner workings of my database need to be changed in order to be 
supported by 9?

This question will come later of course:
How do I make an old site created in pre-Manila 5.1.6 accessable by 
Manila once I pull a copy of my present database into my new Frontier 
and get it working?
I've tried searching the archives here but I don't know if any of 
what I found pertains to my problem.


Thanks in advance for any tips and/or links

Nate