As they are used on many models, they may well look fine on most and changing them may have an adverse effect on those. A good add-on aircraft should never alter the default effects, but there are some that do. If the model in question does use custom effects, the you only need to replace the effect with a new one without faffing about with notepad / MCX. One thing to note is that if an effect is called up in both the exterior and interior mdls, FSX will display both at the same time, effectively doubling the brightness. If that happens, I usually change the interior model to point to a dummy effect that does nothing. You can point it to a non-existing effect which also works, but then FSX will waste time looking for a file that doesn't exist, which isn't good practice.
