[Vibrant Q&A, Help & Troubleshooting] firefly6240:
the best place to start is here

thats a great guide written by s15274n.

but I'll try to answer some of your questions..

Q1 - there are 2 official firmwares out at this moment JFD (which you have) and JI6

Both of these are android 2.1 firmwares.

Some people see better gps lock times with JI6.

Most people also say it drains the battery faster

There are some extra apps on JI6 but nothing too spectacularly different.

There are a few unnoficial firmwares available such as JK2 and JK6 which are froyo 2.2 firmwares (the one you said you would like to download is a leaked version of an upcoming official firmware JK6)

So you are one update behind in official firmware or a few behind in unnofficial firmwares.

Thats not really a bad thing though, it just depends on your preference.

Q2 - you probably should not update via kies, but JI6 should be available through Kies mini if you must do it that way.

Q3 - you can use an i9000 rom though this is not recomended.

Especialy if your just starting.

If you use an i9000 ROM, you would need to use a vibrant kernel.

Otherwise the volume buttons will be reversed. (among other bugs).

Eugenes "Macnut" series of roms are based on i9000 source, and work wonderfully as they are.

If you must have an i9000 rom, at least these ROMs are ported specifically to the vibrant.

Q4 - Malaysia uses the 1800 and 900 bands, and the vibrant right out of the box supports 850, 900, 1800, and 1900

So as far as it working on your network, I think you'll be fine as long as your vibrant is sim unlocked.

Q5 - hardware locked is where you cannot get to recovery without using ADB (Android Debug Bridge)

You can check to see if you are hardware locked by trying to reboot into recovery.

To do this, turn the phone off and boot up while holding both volume up and volume down and the power button.

you can let go of the power button when you see the vibrant logo.

This should bring you to a recovery menu, although for some people, holding all of the buttons is pretty hard so dont get frustrated if it doesent work the first couple of times.

Sim Lock is where your phone is locked to a specific carrier (for the vibrant this is usualy t-mobile)

If you need to use the phone on a network besides t-mobile you will need to unlock it (if it is not unlocked already)

You can check the unlock status by opening the dialer and entering this number: *#7465256#

If entered correctly you will not have to hit dial, it will automaticaly bring up a menu when you enter the last # sign.

if everything in the list that pops up says "OFF" then your phone is unlocked, otherwise you are probably locked to t-mobile, and will need to unlock the phone to use it on another carrier.

Q6 - I dont think there would be any difficulties using whichever rom you like, although everything will obviously be in english.

Some apps do have language packs and such, so I'm not completly sure how difficult it will be as far as language barriers, but the phone will likely work fine (although there are some phone companies who's sim cards just dont work in the vibrant... mostly pay as you go ones)

Q7 - I'm not sure about languages, I've never used anything but english...

Q8 - Clockworkmod is a replacement recovery.

If you are rooted, all you need to do is get a hold of the rom manager app and hit the first option (flash clockworkmod recovery) then hit reboot into recovery (the second choice) and lastly hit reinstall packages while in the stock recovery menu.

You can probably find rom manager on this forum, if not I can find it for you if you need it.

Hopefully that helps a bit...

If not just keep asking and I will answer as best as I can, also read that guide at the top of my post, its a really good place to start.