Please bear in mind I have zero experience with this particular engine however…
White smoke in the manner you describe sounds more like there is water leaking into the cylinder(s) and what you are seeing is actually steam.
Common causes are blown head gasket, cracked head or in some cases a leaky inlet manifold gasket.
Driving a vehicle with this problem will usually lead to more serious issues, and if ignored can be catastrophic in some cases.

Worn valve guides/valve stem seals will cause blue smoke which is usually seen as a plume on initial startup or when the engine has been idling for a while and you accelerate away.
If the problem is valve guides, it won’t affect anything except use a little more oil, so as long as the correct oil level is maintained it shouldn’t cause any other issues.
Valve guide issues don’t usually start suddenly; they normally start a little (small puff of blue smoke on startup), and gradually get worse over time.
85K is a little young to be seeing valve guide issues.
I would try to find a reputable independent repair shop that should be able to diagnose the problem correctly. Others on here might be able to provide recommendations in your area.