Any homeowner who knows how to use a screwdriver and is willing to carefully read and follow written directions can install a programmable thermostat. As others have pointed out, this is low voltage wiring with no chance of shock or electrocution.
But if you are uneasy about even this easy job, call an HVAC contractor and have them do it. They can also explain how to program it (though, again, this is all in the instructions that come with the unit.) Depending on where you live, this can cost from $75 to over $300. Check with your power or gas company to see if they have any special programs -- some have bonuses or customer assistance plans for installing energy saving devices like this in your home. Look on the paperwork that comes with your monthly bills or call the utility's customer service department. You may even be eligible for State or Federal tax breaks for installing the programmable stat.
I've installed these in my own homes and for friends and family (of course, I'm a licensed electrician but that really has no bearing on it). Even my 70 year old mom installed one by herself (i lived out of town then). This isn't rocket science. And, yes, they are pretty much all interchangeable.