Whether you want to download it onto your computer or onto the PSP itself, then yes. It's just like any other large game file you download from the internet... you need access to a wifi network.
Google Earth no longer accepts nor uses user-generated buildings. The old ones are still available through 3D warehouse, but I don't know there's an option to download a few blocks...
The package size is 6.08GB, so a 1 MB/s, it will take about 14 hours and 30 minutes. However, you can continue to do other things in the background, but...