It's unlikely but possible worms still exist. Suspect wood is generally treated by storing at high temperature or with chemicals.

High temps ... wrap it in black plastic and put it in the sun to bake for a while, or find a paint shop that does heat-catalysis of paints and borrow their heating booth.

Depending on species, yes, they can spread.

Was the dead tree on your property? If so, I wouldn't worry about (additional) infestations because you probably already have them in anything that is susceptible to them. :)

I'd cook it as suggested above and keep an eye out for new beetles in the shop.