Blue smoke

but never been fuurther than a tappet in the engine.If you are not using oil and the smoke only lasts for 10 seconds or so and you get no more smoke later, then I would ignore it.
If the guides were worn, you would also be getting smoke on the overrun.
Are the plugs getting fouled up? Again if not, ignore.

If it aint really broke, don't pay out wads to fix it.
(Unless you are a perfectionist, and insist on everything being perfect regardless of cost).

Even if the guides are a little worn, and it will only be a little at this point, they will go on for some time yet.,,,