When I change my vac modulator o-ring, is it wise to change the vac modulator too? My car shifts fine, so i have no rason to think the modulator itself is bad. Would i have to readjust the one i have in there after replacing the o-ring? Or only if i got a new modualtor? I dont like the idea of adjusting it...seems too complicated.

Adjusting the modulator is the easiest thing you will do. Don't worry about that.
Hardest part will be alternately test driving and then climbing under the car to reset the modulator. But it is not likely you would need to reset with just an o ring replacement.