[Vibrant Q&A, Help & Troubleshooting] DrgnAK:
In any case that your local repair shop can't help you too much, I was actually following the directions on these two guides:

http://xdaforums.com/showthread.php?t=1665123

http://xdaforums.com/showthread.php?t=1447303

Mostly the first one. I had already formatted a 32 GB microSD to be my new home for Android. The only problem is the wall I hit in following these directions after flashing to stock (natural reaction for me in this situation if I can't reflash the ROM I am currently using).

To sum up what I did in trying to get a recovery menu that could flash my update.zip for CWM... I did repeat some of these steps to assure myself it wasn't a bad flash:

I was already at stock with the "T959UVJFD.tar" with a GB bootloader. You may be able to just skip to one of the other steps I did without flashing all these other ROMS.

I used Eugene's ROM "Eugene373_GalaxyS_Froyo_PDA.tar" last updated in 2010 from AndroidSpin and was able to boot after getting ADB to reboot it I believe since the recovery menu is unselectable and I had to use ADB while I was here to get to a home screen. I didn't check the stickied threads for Eugene apparently. Pretty stupid. The good thing was that after restarting, I got to a home screen for once.

I flashed stock afterwards and this time it worked. However, Android recovery didn't work, and I usually flash update.zip with CWM from here.

I followed CM's guide to flash Android and flashed Cmenard's kernel using Heimdall, and this resulted in nothing working, only Overstock logo appearing and the phone turning off or resetting afterwards. "This guide assumes the Samsung Vibrant already has Android 2.2 build UVKB5 already installed on it." This may have been the reason why it didn't work. Not sure.

I believe around here I flashed back to a Froyo bootloader.

I flashed a different Eugene ROM found here in the bible thread. I don't remember what happened at this point.

After that, I flashed Cmenard's kernel using Heimdall again and what do you know, it worked this time, in reference to the part where "I somehow got Overstock to work." It may have been because I flashed the other Eugene's ROM first. I could use e2 recovery at this point.

At this point I was frustrated as heck as to why update.zip wouldn't flash, but I later check my SD and found that I never had update.zip on there... Or it was reformatted along the way. So I put all the files I need back on there and continued along the first guide. I flashed GB bootloaders around this point and I flashed CM10 instead of CM9.

After flashing CM10 and getting the welcome message, I went ahead and flashed Semaphore.

I flashed slimbean again since I really like that ROM.

The last step was to modify the vold.fstab file and that was really just a pain. You can use es file browser or w/e root browser you'd like to use but you can easily break the boot sequence if you do it wrong so I ended up modifying the zips and reflashing over and over, around 6 times.

The original:

# internal sdcard
dev_mount emmc /storage/sdcard1 auto /devices/platform/s3c-sdhci.2/mmc_host/mmc2

# external sdcard
dev_mount sdcard /storage/sdcard0 1 /devices/platform/s3c-sdhci.0/mmc_host/mmc0

My modification:

# internal sdcard
dev_mount emmc /storage/sdcard1 auto /devices/platform/s3c-sdhci.0/mmc_host/mmc0

# external sdcard
dev_mount sdcard /storage/sdcard0 1 /devices/platform/s3c-sdhci.2/mmc_host/mmc2

I noticed the two guides above were different and they didn't work. If this explains anything, my SD card was partitioned to 1 ~30GB space and 1 ~2 GB space following that partition. I have no idea why the above guide's vold.fstab modifications didn't work while mine did. I don't even have any experience in doing this junk.

Hopefully this clears up some of the things I did since my original post was a bunch of edits. I hope things work out for you... And if your local repair shop can fix it, I'd like to hear how they fixed/diagnosed it. And that was my night that lasted until like 4 in the morning.