It depends on the operation, if you've never done ANY operations before, I would start by using the GF to queue up for KP and EV Storymodes, just so you can get the feel of it.
Definitely--Group Finder. And if you get people vote-kicking you, then /ignore them so you don't run into elitist snobs.
Eternity Vault Story Mode can be done in pretty much straight level 50 gear, easily done in Tionese (rank 51). Easily.
All of the Story Mode Ops have been set up so that nothing more than 56 ranked gear is needed, as long as you learn the mechanics.
And on that note--might want to check up on the mechanics, or at least ask for an overview of what happens before each fight. There are lots of neat mechanics to each one, and they are very easy to learn and execute...but helps to have some idea of what you are looking for to speed things along.
You'll have no problems, though; groupfinder it and have fun~ Welcome to Ops!!