Got it now! You don't have anything that could be considered a restorable rifle. So there is no question of losing an original. But barrel and stock will not be cheap if they are any good for shooting. So why not just sell the parts?
If you really want to do it for the exercise, and can get hold of a barrel shroud that has become useless (the tubes are often rusted through), then I think you will find that the basic tube is soft-soldered on to the threaded portion with the lug. Unsolder the wrecked tube, but do not saw off the lug, as it takes the front trigger guard screw!
As to the barrel, the thread for the Gew.88 is probably the same as the "small ring" Mausers, such as the M1896 Swede. Please check this very carefully with a gunsmith before proceeding, but if so, it increases your chances of finding a good barrel enormously!