Valve guide replacement will have to be done by a machine shop, I'd not try it at home.
You may need other work too -- worn valve guides usually mean worn valve since they seat off angle when the guides are worn.
Could be oil getting into the intake, too, though.
I always recommend driving a car long enough to get it completely warmed up in cold climates. I lived in Sault Ste. Marie, Ontario, Canada, so I know what you mean by cold winters!
You should only use the car if you can drive it long enough to get the interior completely warm -- this means everything else is, too. Oil won't circulate properly in a cold engine, and you get water condensing into the crankcase as well. It becomes acidic from combustion products, and corrodes things. Driving until the engine gets hot evaporates the water.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!