[Fizzlemizz]

From the 8.1 documentation about the event

CHAT_MSG_GUILD
PAYLOAD:
	text, Type = string, Nilable = false
	playerName, Type = string, Nilable = false
	languageName, Type = string, Nilable = false
	channelName, Type = string, Nilable = false
	playerName2, Type = string, Nilable = false
	specialFlags, Type = string, Nilable = false
	zoneChannelID, Type = number, Nilable = false
	channelIndex, Type = number, Nilable = false
	channelBaseName, Type = string, Nilable = false
	unused, Type = number, Nilable = false
	lineID, Type = number, Nilable = false
	guid, Type = string, Nilable = false
	bnSenderID, Type = number, Nilable = false
	isMobile, Type = bool, Nilable = false
	isSubtitle, Type = bool, Nilable = false
	hideSenderInLetterbox, Type = bool, Nilable = false
	supressRaidIcons, Type = bool, Nilable = false

arg1 would be the text, arg2 the player name. Mind you, it doesn't appear to have changed from 8.0.1.