I have a has fireplace that is turned on by a light switch. It only turns on the unit...doesn't control the height of the flame. What I want to know is can I change the light switch to a remote switch and if so will a dimmer remote switch work since that is all I have been able to find
No. You probably won't find a way to remotely adjust the height of the flame, however a lot of gas fireplaces do have the option of a remote with on/off control and thermostat. This would be an option specific to your fireplace, you'll have to check with the manufacturer to see what's available.