Coding help

Hey, so i have a DarkRP server and everything is kinda finish exept 3 things, 1.i dont know how to code which weapons a gun dealer can sell 2.how to let people buy entites in the f4 menu [I had the play to add some defense lmg's or traps] and 3. how to add a new mayor since i want to give him an other skin etc....so if you know how to do it i would love to get it from you guys !