Read the guide again and you'll find out

 

Oh! I didn't think about using a fresh SD Card! That's...pretty obvious actually, in hindsight...
The only thing is, I kind of want to replace Gateway with A9LH. I mean, it sounds like it's superior anyways. Is there even any advantages of using Gateway over A9LH? It especially pertains to me, because as an ambassador 3DS user, I haven't been able to play my GBA games since I've originally homebrewed my 3DS, and I've heard that A9LH supports GBA games. Besides, it sounds like Gateway is gonna support A9LH (relatively) soon anyways, so it sounds like A9LH is the way to go. I've been using Gateway for a while now, but the last year, (give or take) I primarily use .CIA files and the homebrew launcher, (for homebrew games and some emulators) both of which A9LH can do.

So is there any way that I can install A9LH and still keep my saves, CIAs, Nintendo Network ID, ect.? My initial idea was to restore my Gateway EmuNAND into my current SysNAND, and then follow that linked guide as if that was my initial SysNAND.

(EDIT: Oh shoot! I completely forgot to mention! I'm not sure if this is relevant, but way back when, I System Transferred my Old 3DS EmuNAND to my New 3DS EmuNAND, [which of course was a backup of the New 3DS's SysNAND, as all EmuNANDs are] and that's the current EmuNAND I'm using on my New 3DS to this day. Hence why I have the Ambassador games. Not sure if that will contribute to it bricking or something if I restore it to SysNAND.)

EDIT: Come to think of it, could I use OTPHelper to clone my current Gateway EmuNAND onto my SysNAND? Or is Gateway's EmuNAND different from the RedNAND that the guide asks you to use?

 

Not sure at what point you are now.
I think you have done nothing in the way of a9lh right?

Well when you follow the guide, it says, that you have to do a hole backup of your SD-Card contend and backup of your SysNand and EmuNand.
If you do this, all can be restored as it was.

The GW EmuNand is ok for that. I did the dump with three o3ds units and it worked well with the GW EmuNand.

But please dont perform a EmuNand to SysNand transfere before you have setup the (hole) a9lh installation. That will otherwise brick your 3DS.

 

I guess you're asking something like I did days ago, to go from CFW to a9lh:
https://gbatemp.net/threads/switching-cfw-n3ds-with-10-7-emunand-to-arm9loaderhax.422105/

 

Thanks for all of the replies! So essentially, for the sake of the A9LH guide anyways, there is no difference between RedNAND and EmuNAND? Following the guide as close as possible, I can basically just restore my own GW EmuNAND backup to SysNAND towards the end of the guide instead of using the previously created RedNAND, huh?

Thank you for this link pedroren, that answered a lot of my questions! Specifically about this comment that frosty5689 made:
"1. Backup EmuNAND using EmuNAND9 (latest ver)
2. Copy all content from SD Card (including the emunand.bin) to PC
3. Do a complete setup of RedNAND using EmuNAND9 (latest)
4. Restore RedNAND from emunand.bin"
I believe I will follow these steps during the process, that seems the most fail proof to me.

...Oh, come to think of it, would it be better if I used a separate Micro SD Card entirely as sweatbox recommended during the actual process of downgrading, getting the otp, ect., and then restoring my current EmuNAND to my (by then hacked) A9LH SysNAND? I will probably do all of this tomorrow, (or Friday, if I run out of time) does anyone have any other recommendations/warnings before I take the plunge? I know the guide is specific, I just want to keep my saves and everything, and I hope that I won't do anything stupid and irreversible by accident!

 

Alright, thank you. I will follow your advice as soon as I can. And thank you for the IRC suggestion, but I think that I can handle it myself. Now that I understand it better, it's pretty straightforward.

EDIT: Alright, I did this technique exactly, (although I had to jump around in the guide somewhat. Mostly just to get some of the downloads from an earlier part of the guide) and it worked flawlessly! Thank you very much everyone!

...Oh...while I'm at it, this is somewhat off-topic, but hopefully not enough to warrant making a whole new thread. If so, I apologize. Anyways, I just remembered that I also have an Old 3DS of my own that I would like to put A9LH on, however it's still at good ol' SysNAND 4.5 Firmware from the "old" Gateway days. I still haven't updated it. Anyways, I imagine following these same steps to keep it's current EmuNAND data will work fine, so that's okay. My only concern is that the guide assumes that you're on SysNAND Firmware 9.0-9.2, or at least above that so that you could downgrade. So my question is, how do I get my 4.5 3DS to 9.0-9.2? Should I update it just to downgrade it again? Or should I use a retail cartridge? And if so, is there any games that have that firmware on them to update my 3DS TO 9.0-9.2? not past it?