My Armstrong Ultra 80 SX central furnace (gas powered and over 10 years old) makes loud popping sounds and appears to have a hard time lighting up occasionally. Does this require the replacement of a part?

No it requires you to call for local on site service. Gas is nothing to play with when making this kind of sound especially when it is also having a hard time lighting off. For your safety make that call .

Yeah... what he said.. danger.