GPS or good maps program

Ok so i got this new job and part of what I have to do is deliver pizzas.... well the problem is that i SUCK w/ directions, so im going to have problems finding these houses i have to deliver to! So0o my question is how hard is it to get GPS on my DS, and what would I have to buy to use it w/ my R4 DS? And if thats not possible then is there any good homebrew programs that use google maps or something so0o i can just put a map of the town on my DS?

I think there's actually a program that utilizes Yahoo Maps, but I forgot the name of it unfortunately.

The only other solution would be to use the official Opera DS browser to view Google Maps (I haven't tested to see if it works or not).

Anyone know the yahoo! maps program?