When I replaced my valvecover gasket , it was at 148,000, and there was nowhere near that much sludge. The previous owner must not have changed oil very often...
If It were me, I'd pull the head, take it to a reputable machine shop. Have them do a valve job.They will clean it up, and magnaflux it to make sure theres no cracks.
Reman Cylinder haed is an option,too..
97 Wrangler - 4 Angry Hamsters; 2 1/2 " Rough Country Suspension, 32x11.5x15 Hankook Dynapro MT's.
2011 JK "Mojave".
Recognize the same mistakes, every time you make them !