First off, backup your sysNAND if you are below 9.2.
PERIOD.
You can do this with LOADER.DAT from GW's Ultra Pack 3.1.x.
Second, to get from 4.5 to 9.2 sysNAND without going bast, you'll need to run a game with the 9.2 FW update.
Best example I know of is the 1201 Super Smash Bros. ROM. Not the REV A version. That'll only go up to 8.1.
Last, if you're running on 4.5 use GW menu (loader.dat) to format emuNAND (remember, erases all SD data) and then put rxTools on your SD and boot into rxMode and update emuNAND to latest firmware (9.7.x) Then update everything in emuNAND and the use rxTools to export emuNAND moveable.sed and ticket.dg. Then use rxTools to import those to sysNAND. Now your sysNAND is all updated and patched but still reads 9.2 FW.
WARNING: DO NOT UPDATE ANYTHING UNTIL YOU CHECK SETTINGS AND IT READS "RX-E" IN FRONT OF FW VERSION (much like GW3D for Gateway emuNAND).
But if you're on 4.5, you're golden. You can use Gateway with 4.5 and update the Gateway emuNAND to 9.7. Again, make sure it says GW3D on the firmware before doing a system update. If it doesn't --YOU ARE IN SYSNAND--- and once you go past 9.2 there's no way to downgrade unless you already made a sysNAND backup and then did a hard-mod to the 3DS to then downgrade it.
But you have several options, even without a Gateway 3DS. Remember, you can still use most of their software without the cartridges. But go get your Gateway 3DS carts and backup while you wait. Best option.
You can even dump ROMs and SAVEDATA using the Gateway Menu. Only problem is that rxTools doesn't do homebrew like Gateway does. But it will do system transfers and get you all updated and patched up without hurting your sysNAND.