Usually the filter is right on the inside of where the return air duct meets with the furnace. You usually have to take off the side or front panels of the furnace to gain access to where the filter is. Usually these involve sliding them up and out but it can vary. Check an online owners manual for the make and model of your furnace. Usually there will be a plate of information somewhere on the casing of the furnace with this information.
You can find a schematic for a gas furnace on the website, Uncionradio.
There are many places to find gas furnace prices. One can look on sites like Furnace Price Guides, Century Gas Furnace, and Consumer Reports. One can also find gas furnace prices by going to a local heating supply store.
One could find information on gas furnace troubleshooting online at Ask. Hvac for beginners is also a great place to look. One could also contact their local gas furnace dealer and/or repairer for gas furnace troubleshooting.
What kind of vehicle are you looking at?
an electric furnace runs off of 208/230 Volts while a typical gas furnace runs off of 120 also a gas furnace will have a valve for the gas relay where the gas enters the furnace.
16 x 20
You won't find a gas filter on a diesel engine.
On the inside of one of the removable panels
A person can find a gas furnace in dozens of home improvement stores nationwide, like Home Depot, Sears, Lowe's, Energy Star and many other professional home improvement stores.
How do I get the age of a Trane gas furance TDD100C948B0 or Serial J15538721
On the inside of the blower panel door.
You should not run gas from the furnace to any appliances.