Hi there and welcome to the group. I have a 2020 294RL, so almost same unit. Your furnace is located on the driver side immediately aft of the water heater. Just look for the exhaust port it's easy to find. If you need access, the outside panel comes off giving you access to the furnace from the outside. If you take off the drivers side aft basement wall panel in your storage compartment, you can see the furnace and ducting in your basement, behind the water heater. Hope this helps.
2019 GMC 3500HD 6.6L 4x4 SRW