Does anyone happen to know if there are any significant differences between a Lopi Liberty from 1999 we may be inheriting soon, vs a brand new model? Likely purchasing a house soon with a Liberty installed, but I'm not quite sure how applicable the current Liberty manual is (dated 2013) vs the 1999 model. I am interested in an outdoor air intake and if their new push button "Green Start" thing could be retrofit to the 1999 model but I should probably just ask Lopi directly I suppose.