i wouldn't install any new touch hole liner without first removing the breech plug, IF the breech plug can be removed.
this has never been a problem for me with a traditional breech plug - i use a rice breech wrench and rice octo vise plates.
this CAN be a real problem for most of those production patent breeches, like traditions and cva (they are practically welded on and the manufacturers advise that attempting to remove will bugger the barrel), and add in pedersoli. investarms (lyman, dgw and the like) can be removed with a good flat jawed wrench (reed rcorp) and a heavy bench vise.
also, all liners and plugs go back with anti-seize lube.