Saving App Data for Restore

[xDestructionx]

I have a iPod Touch 3.1.3, jailbroken using spirit. I use iPhone Folders to browse the folders in my iPod.

If I want to upgrade to iOS 4 and then rejailbreak, but at the same time keep my third party app data, what files do I copy?

(btw most of my apps were not downloaded from cydia)

i figure it is somewhere in User > Applications, although i would like instructions regarding what files to copy. would i just be able to copy the whole folder, and then paste it back after rejailbreak? or is there more than one folder?

Thanks pplz,


--EDIT--

ok so i did some looking around, and i think i found out which folders i need to copy, using iPhone Folders, and then paste back after the rejailbreak. i just need some confirmation, please and thank you

private > var > mobile > Applications

also User > Applications and var > mobile > Applications have the same things, but am i correct in saying that these folders are just shortcuts to the folder private > var > mobile > Applications, and that replacing this one folder will change them all?

also what is meant by giving or changing permissions? i do not have to worry about that, correct?