Having started as a pianist (and still one) who has learned guitar, my best advice is to forget the piano keyboard when thinking about the guitar fretboard. It is unhelpful. You just have to learn anew where to put your fingers and practice, practice, practice.
Regarding chords and harmonies; it's useful to be able to visualise chords and chord progressions on the keyboard. It helps with knowing which chords to play on the guitar, but doesn't help with knowing how to fret them.
You just have to learn the shapes for the chords you need. If you want to play melody, you need to learn the scales.
There are plenty on here who will give advice on these things.
Last edited by Stonebridge (2010-01-01 11:38:32)