Question about packet encryption for Private Servers..

Im sorta sure Im right about this...but If Im not...plz dont flame.

If someone makes an emu for a game...dont they need to decrypt packets in order to get the information about certain things? If so...wouldnt the packets ingame on the private server be decrypted...or...is that done by default for that game?

If this doesnt make much sense...Im sry, lol. Just trying to find a way to edit packets on private servers easily...w/o learning how to decrypt on my own (I R teh LaZy! =P)