If you are going darker in color and the finish seems thin enough, you can simply sand the existing finish and apply the new color on top of it. It is even possible to go lighter, it will just take more coats to achieve the color you want. My ears are not this good, but some claim that they can hear the tone difference that finishes induce in guitars, so you may want to keep coats to a minimum...but that's up to you. There is also the weight factor that each coat will add to your instrument. Personally, I don't like to do more than is needed for any given task...less is more school of thought, but once again that is a personal choice. Anyway...back to the subject, you don't need to take the finish off, just rough it up so the new finish has something to grip. Unless you have a high end guitar, factory finishes are generally thin (not too many coats) to keep costs down and maximize profit so painting over the old finish should be fine. This is the easiest way to refinish an instrument IMO...Rog