Syncing phone(s) with 2005 Prius

I have a 2005 Prius which I love - never gives us any trouble. However, I have a question regarding whether or ot I can sync more than one phone in my Prius. I am the primary driver, and my phone is synced with the Bluetooth. But sometimes my husband drives, or we are both in the car together, and in woulde be nice to be able to sync his phone also, so that we are both hands-free always in the car.

On a related question, is there any way to change the disk in the guidance system without paying over $400, which was the price I was quoted? That seems outrageous - I could buy a Garmin or other guidance device for a fraction of that, but since we already have GPS installed, it seems a shame not to use it. I only have the use of one hand due to a stroke (ruptured aneurysm) 20 years ago, so I would never answer a hand-held phone in the car.

I find the instructions in the 2005 Navigation System Owner's Manual difficult to follow. I appreciate any advice.