upgrading PD and Mac OSX together

Hi
I'm looking for advice on method / procedure to make the following upgrades to my system. Bear in mind the compatibilities of my older versions....and I don't have access to the windows disc for a complete re-install so I must avoid this.

Upgrade Mac OSX on my Macbokpro from 10.5 to 10.6 to 10.8 (note 10.6 cannot be skipped)
upgrade Parallels Desktop with windows XP SP3 now running in VM, from v5 to v8,

In what order should I do the steps?
thanks
MB