You can just copy the map.img files off the device onto your PC, where you can restore them from if you did a boo-boo.
The following is assuming the 1030 comes with pretty much the same mapping as my newish 830, which is OSM-derived cycle maps.
You can see what maps you have (on th8 810 anyway, I think the 1030 is very similar) by navigating to Home Page > Hamburger menu(bottom left) > Activity Profiles > Road > Navigation > Map > Map information. It rather unhelpfully does not tell you which .omg files each is coming from...
There are certain map files you should never remove, here's a non-exhaustive list of them. They will all be fairly small compared to the main maps:
gmapbmap.img -this is the base map It contains no detail, but should not be deleted.
gmapdem.img - Digital Elevation Model. Leave it alone.
gmapgc.img - Postcodes,POI etc. Leave it alone.
gmaptz.img - Timezone data. Used to set your local timezone automagically. Leave it alone.
The actual maps are:
gmapprom.img
gmapprom2/3/4 etc .img
gmapsupp.img
Numbered .img files like D6017070A.img are, I think, maps you have purchased and installed from the Garmin website using Garmin Connect.
Corresponding .gma files are unlock files to unlock the maps to your specific device, and can be removed along with their associated .img files.
These can be removed as you wish, then go look at the 'Maps Information' page on the device to see what you have lost.
FWIW, my 830 has 4G free out of 15G. I'd not sweat it.
Best of luck!