Welcome back!
I am a returning player as well and felt so lost when coming back. So far I'm diving back in pretty well and I'll just let you know kind of where I went from day 1 to now.
First off, I had received the email returning players get with a redeemable code on the ncsoft/bns website when you login. That will help with catching up on the equipment (so hopefully you did get that email for returning players). When you login and are choosing the equipment from each chest- don't forget to kind of google around which option would be the best for your playstyle/just best in general.
Next, the best thing to do is just those shiny yellow and orange quests. Follow that story quest like a rabid dog for meat. Not only does it help you get back into the gist of the mechanics, but it also gives you new outfits as well as a better feel and exploration for the newer areas that have been added on over the years. As you're going through those, pick up the blue quests that are not dailies (they're solid blue arrows over the NPCs head or in the quest list J) and complete those in the area for exp and a bit of money.
After you've gone through that, take a look (my BFF is google) at what equipment/upgrades you'll need for end-game, higher dungeons. Also- ASK YOUR FACTION! Not sure what server/faction you are but if there are people they can be very very helpful to returning players. Some even whip across to your location just to help you with a boss. The community is still very much alive in some parts and always willing to help.
Good luck and best of wishes!