Let me give a rough idea of how contributor contribution being transfer to new map by our great mappers!
Let say the contribution is not going to attached the gdb file and just give coordinate, this is what mapper will do
1. Fire up mapedit
2. Go to position - enter the coordinates.
3. if the coordinates end up middle of the road then our mapper will

which position is correct left or right?
4. after thinking thinking put left, but actual is right, release in new map, then kena bamboo by user.
5. Open again mapedit, re-correct back again. (2nd time job!)
6. Let say contributor submit more than one, therefore the process of 1 to 5 will repeat on how many contributor submit the coordinates.
Let say contributor provide gdb file, this is what mapper will do.
1. Fire up mapedit,
2. add file of contributor
3. Check and edit
4. straight away save
So, is good that you have mapsource and learn of how to transfer your save poi and use mapsource to edit it and also for submission. Others contributor POI also can be transfer to your unit using mapsource too.
Cheers!