I thought that I would release my weapon mod but I'm unsure how in the geck I would create weapon mods for the guns I wish to implement in game.

What are you adding to your weapons? you may need nifscope

I've got all the meshes ready as I prepared them in nifskope and I now just need to include the weapon mods into the geck but I'm not sure how.

Go into the Item window. Then find weapons and right click new and boom. Also you can overwrite the vanilla weapons by double clicking them. And you can change their meshes by going into its art and sound Tab. Make sure to rename the gun to your liking so you wont over write the vanilla gun. There you have it