Google Maps is not available to download from BlackBerry World.
Sideloading involves taking a modified Android program and using a PC program to load it manually to your device. Necessary with the PlayBook because many popular apps aren't available.
Someone on the forum said that going directly to maps.google.com works well too.
Thanks! I had not realized the website works so well for searching and such. Navigation is fine on the stock maps, which I'm sure will have a ton of improvements on the future, and hopefully by that time, BB10 will be popular enough for Google to release Google maps on it.