but I don't know if the iPhoto Library is already modified such that iPhoto 6 will not recognize it.
It is. You will need a version of the Library in v6 format for that to work.
And it still might not... As well as jumping 4 versions of iPhoto you've also jumped 2 versions of the OS and there have been changes there too - not least in the Printer Drivers.
What printer do you have?