I am about to attempt some drywalling for the first time and have a question about seams at inside corners, especially seams at the wall/ceiling intersection. I assume that it is desirable to have the untapered edges of drywall meet at these points -- true? Is there any particular difficulty in taping and mudding a tapered/tapered or a tapered/untapered seam in these corners? Thanks!

I am looking to finish my girlfriend's attic (in a 1 1/2 story house, it's the half-story) and am wondering if the "paneling" that is currently on the walls would serve as proper insulation. The paneling appears to be made of compressed cellulose, and is 1/2" thick, and has been there since she moved in to the house 4 years ago. She has asked a friend of hers, who also does drywall, if this would be adequate insulation, and he stated it would and that we should just drywall over it. This would definitely save us time and money if we did, but is this a normal practice? Likewise, if we do drywall over it, what would be the method of "trueing up" the new drywall surface with the window and door frames?