Yes, you can "Undo" a Jailbreak, by going into iTunes and Restoring your iPod Touch, or iPhone.
Yes, there even going to soon make a jailbreak for iOS 4.0
if you want your iPod touch jail broken you could go to a computer store and ask them to get it jail broken
How to jailbreak my iPod touch
Try going on youtube and they will give you a full guide
to jailbreak your iPod 4.1 go to greenpois0n.com
No it will restore itself and there is currently no jailbreak for 4.0 so stick with 3.1.3.
Try going on youtube and they will give you a full guide
No. Your jailbreak will remain as it is. Syncing your iPod does not alter the jailbreak in any way.
Yeah of course. It isn't going to make a difference. When you jailbreak your IPod you are going to add an app called Cydia. Which take it from there will give you all the things you can dream of. :D
If you have already successfully completed the jailbreak, then just turn it on as you normally would.
Sucked in fool don't jailbreak