Welcome to the Stoner club!
That is a good price for that machine. You are correct, these machines are very top heavy as the majority of the weight is in the vending rack which is in the top half of the machine. My recommendation would be to put some weight in the base when you get it working if any kids will be using it.
When you get it open, post some pictures of the insides and I am sure the collective wisdom on this site will help you to get it working. There are some Stoner manuals in the download are that will likely be helpful to you.
Tim