so when I do my diff mod do I need a kit? or can I just pop off the 3 screws, clean out all the old grease and fill them up with the silicone and lock the screws back down? any kinda of gasket seal needed to prevent leakage or should I just check them every so often to see if they need to be refilled?

I did my savage diffs and haven't had to touch them since last year.

and also how much am I putting in do I level off the fluid in half the diff cup then cap it? or half way? etc..