just be careful... some effects loop indefinitely, and if ya use one for a
flash, it's stuck to your ship untill ya die, or dock with something.
And yes, changing or switching an effect is much the same as making a new one-- you have to go into effects.ini, find the entry you want to use for your SNAC and substitute it for the effect your weapon currently uses. You can switch effects and sounds fairly easily this way.
I do not recommend that you do this on the Discovery mod. If you want to play around with effects, make your own copy of Vanilla Freelancer (in a separate directory) and mod that.
Arggh...the code format hates walls of text...
You can change the sound of weapons easily. I had my trader guns sound like bs pulse cannons. Pure awesomeness. I haven't gone around to change the effects.