Corrected entry: In 'Bewitched, Bothered And Bewildered' we see the interior of Xander's room, and a guitar is resting against the wall in the background. Next season, in 'The Zeppo', he asks Oz if it's hard to play the guitar. If he already has a guitar you'd assume he knew how to play it, or had at least tried to learn in the past year.
Corrected entry: Third season, Episode 3ABB13-The Zeppo-Jack says that he couldn't raise his dead friends earlier because he "had to wait 8 months for the stars to align," but he died three weeks ago and his grandfather raised him the same night.
Correction: Jack says he was dead less than ten minutes - perhaps that affects the necessary conditions for the spell.
Correction: Xander's character isn't often driven or committed to non-life-threatening causes. In Season 5's "The Replacement," his friends comment that the Xander clone is much more decisive and determined than original Xander. It's quite likely that such a person would pick up a secondhand guitar on a lark but never follow through and learn how to play it - after all, he did fantasize about playing the guitar to impress Buffy way back in "Teacher's Pet."
Phoenix