Is there a function with surface GUIs that allow you to click them and activate an event?

No, but you could insert in a ClickDetector which would work just as well. Lets say that the part the SurfaceGui is adorned to is the scripts parent:

local Obj = script.Parent
local Clicker = Instance.new("ClickDetector")
Clicker.MaxActivationDistance = 1/0
Clicker.Parent = Obj

Clicker.MouseClick:connect(function(Player)
	--What you want to happen here
end)

This would put the ClickDetector in the part that the SurfaceGui is adorned to, then you can put what you want to happen where I put the comment.