Dang it. phflack beat meh to it. Dang computer. ANYWAYS
This might be using another addon, but it's still variables,
1. onActivate>self>ifscore [is greaterthan or is equalto] [score]
2. Varabletrue>namedbrick [spawn]>set vehicle [vehicle]
You can use that, It's a little simpler than the new VCE in my books, But I'm not too good with "setEventEnabled" so you're gonna have to have more than one button that dissapears after the vehicle is upgraded to prevent downgrading.
Also, I think that in that addon is an OnMinigameReset. You can use that to get the buttons back after the minigame resets.
There, That should be it