Not a gunsmith, but...
It's gonna depend on how you go about the whole rig. If you are switching barrels and leaving the gun essentially factory style, then you will need your bench and barrel vises and the machining on each barrel is essentially going to be done as per the factory style. Frequent use of switching the barrels may, eventually, lead to wear that will have to be taken into account. Really long term or frequent usage problem, maybe, or maybe not.
If you go with something along the lines of the Savage system, with a nut on the barrel, then you are using a wrench on the nut and the threads in the action fit accurately, but are able to be essentially screwed in by hand and headspace is adjusted each time the barrel is installed.
Of course, there are dozens of different switch barrel systems out there any of which may strike your fancy too. Some require pretty radical changes to the mechanism, some not so much.
So, essentially, you ask "How long is string?", the answer to which, is, "Long!"
The machining is the same in any case, however the switch is intended to work. Careful, accurate, and workmanlike.
Maybe that answered the question, maybe not.
More information about what you wish to do, and to what end, may get you a less generalized answer.
Cheers
Trev
