JingleMisk

I have FOMM but I have no idea how to edit stuff there. For some reason the edited sniper rifle in the esp file I made is lost and I have to copy, ( I dont want to edit the regular sniper rifle ) or make a new sniper rifle. But it also asks for the ID, so how do I give ID numbers to objects, according to what? So I can easily say "000444" for example?

I am all new to this modding stuff on Fallout 3 and after I wasn't satisfied with a weapon's stats which came with a mod, I wanted to edit it. I opened the mod in GECK, I found the weapon and edited the stats, by increasing the damage. Then I wanted to save the edited mod file but it would only save as .esp format and the mod was .esm so I saved it with a different name anyway and now, naturally the rifle with edited stats is in another mod and the mod I wanted to edit still has the old version of the gun. So my question, how to edit .esm files and then save them :D Thanks in advance people