well first off you need the HomeBrew Channel, there is tons of tutorials out there for the Updated version, just gota do a little searching
HomeBrew Apps needed
-Save game Extractor
-Save game Installer

2nd off if you still have the RVFOREST DATA on the SD card im sure you can just use the Save game installer to install your town back to your old town, that should work from my understanding

Also, you should always have a Backup Save file on your computer incase theirs something wrong in your town