Re-barrelling a Ruger Number One or a Number Three is a little more involved than re-barreling a mauser bolt action.
The barrel mounted rib is removed on a Number One.
A special collet-type barrel wrench is needed to remove/install the barrel. The collet wrench is needed to get around the forearm hanger because it interferes with a regular barrel vise. Many shops are not equiped to do this, and will charge extra to purchase the special tools.
Except for the special collet wrench, fitting, threading, and headspacing are done exactly the same as on Mauser bolt actions.
HTH
John