Ipod touch buying advice!!!

[Treebeard]

Can anyone help? i'm looking into buying an Ipod Touch, 2nd Generation and I wanna be able to jailbreak it.

I have a Mac. is this program any good to use???

http://www.youtube.com/watch?v=mHST8rGTW_4

And if it does work (as my Mac is 10.5.6) is enabling DFU mode easy? Does it affect anything? Can you enable DFU mode using an administrators account but would it still be enabled on a different account?

Is there a better way of going about this? (I don't have access to a PC, only a mac)

And finally,

- Can a Jailbroken Ipod still download and install official apps?

- Can a jailbroken ipod be Un-jailbroken if needs be to take it back if it breaks?

- (I live in the UK) if I bought it from Apple, wold I be able to take it back if jailbroken?

Thanky