On a recent home inspection the inspector noted wood damage to a section of the sill plate at the font wall of the basement near the base of the stairs; replacing the damaged wood is advised.

Can you replace a sill plate or a section of the sill plate in a home that's 64 years old?

Yes you can, but depending on how long the damage piece is will depend on how difficult it will be. Can you send us a pic of the rotten wood?

Glavine is correct. Once you cut the sill plate front to back in the center you can pry it up, both ends will then come lose. The new sill needs to slide under the door frame rails so some fine tuning will be needed. Most carpenters will tell you to use pressure treated lumber for the new plate, you don't want white wood touch concrete.