It's a very common mod. I haven't done it on a Guild but I have on other guitars. My SE-100D seems to be a prime candidate for it as the top end roll off is extremely apparent when the volume is dropped even a few notches (don't know if there are some other funnies happening there as I seem to recall a thread about some strange wiring or pots on some early 60's guitars).
If doing the mod, it pays to experiment with values depending on what you want - e.g. too large a cap value and the guitar may be brighter with the volume turned down than when at full. Of course if this is what you want then that's OK!