I have a Boiler in the basment and a AC Handler in our attic.

Which a thermostat which is prob from the late 70's. I would like to get one that is digital and programable to save some money on our heating and cooling bills.

Can I just get any one that I like or do I have to get a HVAC company to install it since it is not the same unit?

I would like to get one with an outside senser so that we can have it know when it is hot out side to not to keep the heat on if it is above 70 degrees if that is an option. I think I saw that one with Rich on a TOH but not sure where to get that one or a name so that would be great if you know if that would work in this setup as well.