I doubt the lock needs to be changed, nor the steering lock.  In additiion to the lubrication mentioned, many times the lock issues are cause by worn keys, or badly miscut keys due to being a copy of a copy of a copy.  Get the code number and cut a new key from the code. A new copy of trhe existing key does not bring the key back to factory specs.   Also, when you lubricate VW locks, DO NOT use graphite.  It will combine with the grease in the locks and turn to cement.  Use Tri-Flow, which can be found at many bicycle shops.
 
As to whether or not a new lock can be keyed to match, yes it can.  The problem is finding an actual Vanagon lock.  The replacement locks use a different keyway (Key profile) and cannot be made to match.  Actual correct Vanagon locks are getting quite rare.  If there is a problem internally in the lock, it can generally be serviced to restore correct operation.
 
Steve Sandlin, Registered Lodcksmith
www.steveslockshop.com