I found on my furnace the rubber gas line was long enough to reach outside to sawhorses I had the furnace on once I removed it. I bought a 4 prong trailer light plug and connected that into the furnace wiring to make unhooking easier. Now I can unplug/disconnect, remove furnace, place it on the sawhorses, reconnect and easily see it work. While I had it out, I lined the intake air plenum chamber area with automotive underhood sound deadening mats and considerably reduced the noise of the furnace.
Please do not follow the instructions to use a pencil eraser to "clean" contacts. Todays circuit boards have the thinnest amount of material used for contacts and will erase away in no time. Instead find some spray tv tuner cleaner or use a q-tip with some isopropyl alcohol.