I’m a total noob when it comes to scripting, but I need to get this done, because my mod is a total must for me

Scenario:
I have an object ( a sign ) I want this object to be active, so I can click it and get an option. if i click YES a new object will appear next to the sign, and the sign will disappear. I know all this can be done with an X-marker.
I want the sign only to give me the yes/no option if i have a certain object in my inventory, else it will say " you don’t have the object bla bla bla "
This should all be possible with the same system that gives you furniture upgrade option, but I really don’t know where to start.
If there is someone with the brains to help me I will be forever grateful.
Thank you in advance
Nico