Alright, I could make this a quick answer and you'd be happy, but I always feel it's better to make sure you understand what's going on with things.
Every Xbox 360 DVD drive is locked to their Xbox motherboards with a 32-character (16 byte) unique hex drive key. This drive key is contained in the original firmware of your DVD drive. If you were to try and swap a drive from one system to another, without changing the drive keys, neither drive would work. They wouldn't read any discs because the drive keys do not match the motherboards.
So.. think about this for a second. The drive key is on the original firmware. You are trying to flash a new firmware to the drive, overwriting the original firmware that is already on there. In order for this new firmware to even work, you have to get the drive key from your original, injected into the new firmware. Understand?
This is the entire reason why when flashing a Samsung drive, the first step is to backup the firmware (to get your drive key). The second step is running x360sam - this program takes the drive key from your original you just extracted, and injects it into the hacked firmware you want to flash to the drive. Now that your hacked firmare is "ready" because it has your key, you can reboot, and flash the drive.
With that information , apply it to the current situation. You have a flashed drive (which contains your drive key) and you are trying to upgrade the firmware.
The same process can be applied, since the only thing needed is your drive key. Both your original firmware, and the firmware currently on your drive have this. Just do the same samread/samhack as you would if you were first flashing the drive. You do not need to reflash to your original firmware first (they have the same key). You would just be wasting your own time.
With that said, it is always a good idea to keep your original firmware backed up. Email it to yourself. It contains that all-important drive key.
Now, your second question. How to fool the MS28 drive. Well, you can actually use the
0800 disc to disable the FirmGuard/MS28 lockout. Burn this .iso image to a DVD+R DL. Insert it when you are in DOS, let it read for about 20 seconds, then take out the disc. This will temporarily make your drive an MS25 so that you can easily flash the drive without VCC/bad-flash methods.
