Hoping an Expert or someone who's Been-There-Done-That can help. New-used home (1 year) came with ceramic top electric cooktop set in granite. I hate it. Have always had natural gas for cooking. No natural gas available, have convinced DH to let me have piped for LP (hw heater and bbq grill already hard-piped in) Measure cooktop on top, is 29 1/4 x 20 3/8. Metal box underneath is approx. 28 x 20. None of cooktops looking at Home Depot exactly match---is that okay---know need to be a little smaller than existing hole---no one will "re-cut" granite. Also, am told I need to call a PLUMBER (?????) to do the propane piping? Does this sound right? TIA for any advice, suggestions, thoughts.