Hi, I'm new to Garmin here so i will ask many things and might be stupid things for some of you guys, i have a garmin nuvi 310 with "Garmap African Series 2008, southern african"

the task is i wanted to update it to 2012 map so i have updated information about the road and all recreation stuff, restaurant etc

Inside Garmin Device :
Folder POI : inside there is poi.gpi
gmapsupp.img (158 MB.. i think this is the map)
gmapsupp.unl (this is unlocker if not mistaken)

SD Card
Folder Audible : inside empty
Folder JPEG : inside some jpg image
Folder Media : inside empty
Folder MP3 : inside empty
Folder Garmin : many folder and files there
- Folder Diax :
- Folder gpx :
- Folder Help :
- Folder Poi :
- Folder remote SW
- Folder Vehicle :
- Folder Voice :
fs_image.ver
GarminDevice.xml
gmapbmap.img
GUPDATE.GCD

now this is what i've done
1. download Garmap Sub-Saharan Africa Streetmaps 2012.1 NT Version ( I dont know what is the different between Non NT and i dont know which version should I Download)
2. download the Image file "Unlocked NT IMG File" (I think this one same as above since above you need to use mapsource to convert it to IMG then using IMG Unlocker)
3. I have patched latest Mapsource + Latest MapInstall
4. I have IMG Unlocker
5. I've tried to compile the map using mapsource and it is success..but then when i copy it to the Garmin Device it is like error map

question :
1. where should i put the image map? in the device? but what the SD card for? since if i took it out ..the garmin wont work
2. what is the streetmap, topo map etc? do we need all?
3. I just want the road changes as per 2012 road + all info like fuel, restaurant, supermarket etc also changes as per 2012

thanks for reading a very long posting.. and thanks for helping me