..... There is another I am searching for that perhaps you know where it might be? It details using the SD card to have Garmin Express load to it? As I remember, you put a folder named Garmin on the SD and then inside of that folder, you place the file: GarminDevice.xml. Garmin Express will then see the SD card and load the file: GUPDATE.GCD onto the SD card. .......
I don't recall a specific thread for making what's often referred to as "a nuvi clone", or "Garmin stunt-double" as i call it. The steps you outlined in the above are correct and provided the XML file from the device is up to date, GarminExpress (usually) will recognize the USB device as the actual Garmin device and offer appropriate files accordingly. There are exceptions to that however if GE baulks then WebUpdater will work but only for firmware and software downloads and not of course for map files. Note however that the Garmin folder must be in the root of the card. If a .System folder is needed GarminExpress will create it however you can add one beforehand if you want: [Only registered and activated users can see links. ]. The card should be clean other than Garmin and .System root folders, best to format it to FAT32 beforehand. Use a card 32GB or less, larger cards are usually formatted exFAT but can be re-formatted to FAT32 in Windows. The problem you faced with Windows messing up the drivesmart's file system doesn't apply to media cards used in garmin devices. Always use only RMPrepUSB in Windows over the OS's inbuilt tool or any other 3rd party format tool for the internal memory of the device itself. Also never use a Mac or Linux machine to format a Garmin device. They all do it slightly differently, so to mangle an old saying about skinning a cat, "There's more than one way to format in FAT".

Much of the verbose offerings in Garmin's email replies is either inaccurate or not applicable in your case. As for this gem:
"Never format the unit. It will be unusable."
HAHAHA ... Ahhh.... Garmin, Garmin, Garmin ... you are ever so prepared to let your service desk drones spew out partial truths and at times downright misinformation to the trusting and unsuspecting public. "Never" indicates 'not under any circumstances', clearly untrue. This is what they should tell you: "You should not unnecessarily format the unit. If it's already unusable due to an accidental previous inappropriate format or it has numerous file system corruptions (nonsense named files/folders that cannot be renamed or removed for example), then as a last resort (and after re-enabling Mass Storage Mode with cure firmware if required), a format should be done but only using RMPrepUSB with the correct settings. Otherwise just removing any corrupt files from the device is sufficient". Can't expect them to tell you that i suppose, never sell you a new device with 20% off RRP that way. Most discount retailers will offer the same device cheaper anyway in my experience and no shipping charges. BTW, about this quote: "Service for this product is no longer available" ... Service for an individual modern device never was available from Garmin directly, they have in the recent past only ever exchanged returned devices with a 'factory-refurbished' one of the same model and that policy still applies even to 'under-warranty' units. Out of warranty devices may qualify for their replacement program depending on re-furb availability but they hit you up for about 200 bucks plus shipping. The lack of real assistance usually issued by Garmin's "service" desk is the main reason ppl turn to forums like this one for genuine practical help. In fairness some of their service desk personnel are very knowledgeable and go out of their way to help with tailored advice.

P.S. IMPORTANT: Note that your DS may not have a basemap despite being updated with GarmiExpress. Download one to the .System folder from here: [Only registered and activated users can see links. ]. Navigation may fail or be glitchy without a valid gmapbmap.img onboard the device, and high-level map scrolling will crash it.