[Help] .Rez and .DTX Files

Ok, on my journey to become a modder, I have encountered some problems. When I extract the .Rez files, I have a bunch of .DTX. I know what some of them are for because the file have the weapon's name on them. Right now I am taking a chance and trying to mod a SPAS-12 Shotgun into the AA-12 shotgun. When I compared the files, some of them don't match. I searched the files that AA-12 shotgun had and it turns out a lot of Nexon Cash Weapons also have the same files. Now my problem is in the GUNS_PV_M_SG folder, I have ANI_G_AA-12_CH.LTB and a SPAS12_ANIBASE.LTB file. Now, are these 2 files the same or does the ANI_G files have to do with something else? Also, some of the other files don't match as well. I'm not gonna list them out. When I did other mods, the files matched perfectly. I would like to complete this challenging mod. Can you guys help me complete this project?