Is this under warranty if so you may want to start the warranty process early on. It may also help to have them involed as they will ask for specific things to be tested and have reasource to make these test easier to complete.
And if its toast you want them involed in the trouble shooting so you will not have to go back over every little detail again and again just to get it replaced.
Thermostats dont like to be touched after they are installed. Once its in it stays until you replace it with a new one. With that said it is very common for thermostats to hang open or closed and cause all types of problems. Best to go all new when you can.