Currently Being ModeratedSep 4, 2012 3:21 PM (in response to alex hall)
The easiest way for me to send a program change in Logic is to use the Event List to make sure that changes happen at a particular point - usually a break where nothing's happening, to give it time to work.
You want to change the guitar sound at a certain time, but you can achieve the same kind of thing from recording different sounding guitar parts on different tracks, if you're thinking about recording. If you're thinking about changing the guitar sounds when you play live, set it up the way you want it to sound in Logic and save channel strips so that you can use them in Mainstage.
I have an old Line 6 pod that does respond to program change, I got into it for a while but I think there are better ways of doing that kind of thing now depending on what you want to achieve..