How would I change the characteristics of a player model with a button click?

I’m trying to make a shop where you can buy, for example, a different colored wheel. How would I do that, or something like it. Is there some sort of key word? I have the shop GUI set up, but I have no idea how I would make buttons that change the character. Thanks. Here’s the GUI code i have so far:

#pragma strict
var shop : boolean;
var money: float;
function Start () {
    shop = false;
function Update () {
    if(Input.GetKeyDown(KeyCode.Q)) {
       shop = !shop;
       money = 0;
function OnGUI () {
    GUI.color =;
    GUI.Box (Rect (15,30,90,40), "Q: OPENS 


    if(shop) {
        GUI.Box (Rect (110,25,300,300), "SHOP");
        GUI.Label(Rect(120, 35, 60, 20),"Money: " + money);

You can use buttons!