How do Gilman reagents open epoxides? From what it looks like, Gilman reagents are good nucleophiles, and will attack at the less-substituted side of an asymmetric alkane because Gilman reagents don't necessarily need a substantial amount of partial positive character at the site of attack. 

However, don't strong nucleophiles open epoxides in an SN2 like manner? Where's the inversion?
In the first reaction, the reaction doesn't take place at a stereocenter, so there's no way to observe the inversion.

In the second reaction, the stereochemistry in the product is R, R. The Gilman reagent approaches opposite the C-O bond. After bond rotation, we see the product in the indicated conformation.