I am looking to replace my 24 year of zero clearance Fireplace, with a new Heat N Glo 6000CLX. My question is will I have to replace the exhaust venting to accommodate newer standards. The old model is a direct vent unit, that vents through 2 stories and has 2 90 degree elbows> The elbows happen to be unreachable without some serious demo or removing my furnace to gain access to this area. Any information is helpful. Thanks