Lingcod are subject to all kinds of parasites, and also live in a wound-rich environment. Aside from their predacious relatives nipping at them, it's not unusual to find broken-off sea urchin spines embedded in the flesh. Contact with the spines of rockfish could also cause festering in the flesh.
I'd go with the "cut out the bad bit, then cook it well" option. You could add insurance by freezing it for a couple of months first. If you're really worried, after freezing it, you could brine it and smoke it.
I'm with the recommendation to put back lings over 15-20 pounds. While you will certainly find worms in smaller fish, and also parasite-free big ones, the odds are not in your favor with larger fish. The really big ones are female breeders in any case. I shake my head when I see outfitters advertising "Trophy Lingcod". I love lingcod on my plate, but I wouldn't want one on the bedroom wall.