When you touch it, the touch screen is very temperamental. It will easily switch to Celcius and the temperature may go up or down whenever you touch it -- sometimes it's difficult to get it to do what you want it to. I read on Heartland's owners Facebook page where many folks are having the same issues. I think it was Dometic's upgrade that has a few bugs...
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It's possible the older style Single Zone LCD might be plug compatible, but I don't know if that's the case. There's probably a larger problem in that warranty replacements are usually limited to providing the exact same part. It might be difficult to get a different replacement part unless you buy it.
Ebay might be the lowest price.
One way to go would be to ask the dealer to get you a replacement thermostat to deal with the problems you're seeing. Buy the older one and see if it works. If it does, you can sell the new one on Ebay. Maybe you'll break even. The risk is that the old one might not work, and while unlikely, it might cause damage.