he didn't give slash his guitar, but he did show him some chords, slash got his first guitar from his grandma, it had one string. and I wouldn't call him terrible he was great, not amazing but spectacular in his style, but he was always one soul full and from the heart player, his guitar has always been his voice.
For someone who named his youtube account after Slash, you don't really seem to know what you are talking about. You say Slash wasn't very good at the beginning of Guns N' Roses, listen to their first album, its called "Appetite for Destruction". You'll see.
lol ive read his book, duffs book, various Guns N' Roses band biographys read and watched countless interviews and documentaries. and if izzy or Axl would make a book i'd have those read to :P