I'd advice you to just use PFM for that. You might only need the AK for taking a look at how the models you want to use are called. So in PFM you go to New, Right Click, Add from Pack and choose the models .pack. Double click on the unit you want to change. After you have added it you can right click on the Variantmeshdefinition and Open as Text. Then go to the "weapon_02" slot and replace the line beneath with
Code:
<VARIANT_MESH model="VariantMeshes/_VariantModels/man/weapons/nameofyoursword.rigid_model_v2" imposter_model="VariantMeshes/_VariantModels/man/weapons/nameofyoursword.rigid_model_v2" >
Save the mod in your data folder and that should do it.