differential leak and ac refill?
 

Hey all,
I am just wondering how hard it is to replace the rear differential gasket in my mustang. I know it needs 3 quarts of full synthetic oil, silicone for the gasket, a friction modifier, and something to clean off the old gunk. Anything else I need? anything to worry about while doing it?
Also the AC only blows cold when the engine is over 2k rpm's so I think it needs to be refilled. How hard is this? any tips and tricks? are those kits at the parts stores worth getting?
Thanks for the help! :)

Not sure about the diff, as I've never played with them.

The kits will work, just make sure you get the one with the gauge. You don't want to overfill. Yeah, there is a blowoff valve but it is not something that you want to use to set the level.

Thanks, :) Ill be sure to get the right one.