Your post did not say if you have a solid frame or a takedown model 97. You did not mention if you want to go the full trench gun with the heat guard or just want to short barrel. On a solid frame you will unscrew the original barrel and screw on the new one. If you are putting on a real trenchgun barrel it should already have the grove cut for the handguard screw...If you are putting a trenchgun barrel on a takedown model, you can or have a gunsmith try to screw out the original barrel from the collar and then carefully screw in the new barrel. A better way is to buy an extra collar and screw the new barrel in it so you could easily convert the 97 back. The collars can break so care should be done in installing the barrel to it. There are some tricks to fitting the barrels so I would suggest a gunsmith who knows about 97s. If you are going the whole trenchgun route on a takedown you need to buy a couple of extra parts to mount the handguard.