Finale 2006 Sound fonts

I downloaded a soundfont for a guitar and changed it in the setup. Unfortunately, all my other instruments changed as well.

What i was wondering is if there's a way to only change the sound on one instrument and leave the rest as default?

You should load the soundfont only into the preset you want to change. For example, if I want to use my flashy piano soundfont, I load it into preset 0 (grand piano). What you probably did was to load it in as a bank - this results in the entire general MIDI bank being replaced by one single soundfont instrument. If you load it in just as a single preset, the other instruments will stay the same.

thanks, but how do I get to the presets menu?

Unfortunately the only real way to do this is to edit the soundfont itself - it wouldn't be a problem except that it's now difficult to find soundfont editors. If your computer has an SB Live or Audigy soundcard, you can probably still download and use the Vienna Soundfont Studio. I'm not sure if there are any other free soundfont editors available now. Audio Compositor was my favorite but is no longer available from its author.