As a complete greenhorn, I naturally started off by practicing some of my favorite songs by such great artists as U2, Joan Baez, Kris Kristofferson, Sheryl Crow, Metallica, Radiohead, Jason Isbell (and if you think this is quite a jumbled hotchpotch, you haven't even seen half the list...).But of course my guitarist (yeah, need one - who of you really believed that I'd actually learn to play well enough within a couple of months?) isn't too happy with covering other people's songs (no matter how great they are) and suggested writing our own stuff. I said "Nah... -- If -- at…