Double Return on a furnace

We recently purchased a a 95% efficiency furnace to replace our old 80%. The techs at the HVAC supply store said that this furnace will need a second return. It is a 140,000 BTU propane forced hot air furnace. My old one has the return set up on the left side of the furnace and the return vent is in my living room. The return vent takes a 20x30x1 filter. Will the second return have to come out on the right side of the furnace and how do you think the installer will do it? Just wondering if all new duct work will be getting done. I am heading away for work and want to let the boss know what she should expect to happen while I am gone. Thanks

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