I'm using Clockwork, so I'm not sure if this will work for SPR, but I don't see why not. I was able to repeat this twice just to make sure it worked, so here'e the process:
1. Using Root Explorer (or ADB) move Maps.apk to the SD card
2. restart the phone
3. install Maps.apk from the SD card (not from the Market)
4. Go to Settings-->Applications-->Manage Applications-->All and find Maps
5. Click on "Clear Data" and the "Uninstall"
6. You should now be able to go to the Market and install it from there