First take it back and pay them to add die. Or do it yourself. Then use a cheap UV light to find the leak. If you don't see the leak pay them to use a sniffer to find it. Don't forget to put the sniffer in the vents inside in case the leak is occurring in the evaporator.
Second, the controls are NOT $300. I just bought one.
https://www.amazon.com/gp/offer-list...&condition=all
They used to be $40 now they're $100 +-