Does iPhone 3gs have to be jailbroken to unlock it?

I bought used iPhone 3gs and it's on orange.

Do i have to jailbreak it so that it's unlocked?

What's the easiest way to unlock it for an amateur?

No it doesn't have to be jailbroken.

Easiest way would be to buy an unlock code from your carrier.

Yes. Jailbroken is unlocking it.

Heres the easiest way I found.
1st. Back up all of your Data (all the data will be erased when jailbroken)
2nd.go to http://www.spiritjb.com and download the right stuff. Its self explanatory on the website
3rd.hold down the power button and cirlce button for 10 seconds then release the power button adn continue holding the circle button for about 10 more seconds. Then turn your phone on.
4th. You knows its jailbroken if you have 'Installer' and 'Cydia' on your home screen
the risks of jailbreaking are very rare. It is really cool if you do, and its worth it.
if any problems, turn phone off for about 60 seconds and reboot it.

Sometimes its better to have a hitech friend cause they know everything! Lol.

In most cases yes.

http://iclarified.com/unlock should help.

No it doesn't and I don't recommend it for an amateur as it can permanently disable your iPhone. I recommend a factory unlock. There are many providers of unlocks for your carrier online if you do a search.