Hopefully this will give you some ideas & help get you started.
Install
Zgoo Addon
Then hoover your mouse over whatever you want to find out about & type: /zgoo mouse
A window will pop up with all kinds of information. Scroll down to the function GetName() to find the name of the control.
The window will also have other information about that control. Including values it has, child controls, parent controls, functions you can access through it. All kinds of stuff.
Code to change it:
Lua Code:
-- Set up the string I want to display
local newMoneyString = zo_strformat("<<X:1>>|t24:24:EsoUI/Art/currency/currency_gold.dds|t","9,999,999")
-- ZO_PlayerInventoryInfoBarMoney is the control I want to change. I got it from GetName()
-- :SetText is a function that sets the string/text for the control passed to it...the thing before the :
ZO_PlayerInventoryInfoBarMoney:SetText(newMoneyString)
You don't have to use zo_strformat. You could use any string you created.