Free download of RAVE tech and owner's manual below.

 

White smoke in the cold weather is normal, water coming out of the tailpipe is also normal.
95% of all O2 codes on a Discovery are because it needs a tune up, that means new plugs and wires.
Remember that you must use premium gas in these trucks.
Read the entire owners manual to understand your truck and how it all works, there is a cubby hole under the drivers seat, check there if it is not in the glove box, under the passenger seat is the CD changer.

 

OK. So here are the codes--all related to 02 sensor and misfire: 1193,0130,0158,0138,0151,0300,0304,1316,0430. So I'll check wires and plugs, especially cyl. 4. I already saw that there are new looking Bosch platinums in there but the wires look a lot older. I'm no longer worried about head gasket. White smoke goes away and it isn't anywhere near overheating.

Thanks

 

If you think wires look old, they need swap out. You may even be able to see electric discharge at night in the pitch black along the wires. Overheat should be defined in your mind as anything above 9:00 on the gauge, it has a very broad range. Check your fluids weekly. Consider the handy Ultra Gauge, about $70, digital multi function gauge and code reader.