GMP100-3: No ignition

My GMP100-3 ignitor will no longer work. (After several attempts, the furnace will report a one-blink code and stop trying.) Visual inspection also shows no ignition.

If I light the furnace manually during startup, it will stay lit correctly until shutoff. The wiring harnesses seem to be firmly in place.

Do I need a new ignitor, or a new circut board? Can I test the ignition wires w/a DVM during startup - and if so, is it line voltage, or is there a step-up? (I think this is a glow-plug type of ignitor, and not a spark-gap ignitor, correct?)

If a replacement is needed, any ideas on a preferred place to get the parts? -- I'd like to save some $$ over a repair call. It would be nice if I could get a whole new electronics+ingitor set and be able to return whatever I don't use.

thanks