Is there a way I can do that without losing my installed packages, etc?
Only in hindsight.
I think, if I understand your post, that a 64 bit upgrade will need a complete re-do from a 32-bit OS. That's drivers and packages, etc.
The following advice is for things you want to keep despite an OS failure (or change).
When you re-install set up a "/" partition and a "home" partition as well as "swap." Put the OS in the "/" partition and anything you want to keep in the "home" partition. After that, anything you put in the 'home' partition will still be there no matter what you do to the "/" partition.