Throwing caution to the wind (after doing a ton of research), and going with the burnt exhaust valve on cylinder 4. Can someone direct me to a thread that covers the removal and installation (step by step with required tools) for a remanufactured head removal and replacement? (Throwing in a new timi...

New to Volvos. I have a misfire code for cylinder 4 error as well as a P0134 error(O2 sensor no activity , bank 1, sensor 1) guessing the O2 front side is that error. Replaced the plug and coil on cylinder 4, still got both codes. I've heard a misfiring cylinder can ruin an O2 sensor, so I'm trying ...