Returning to GW2, been away since release.
There are a few Full Servers, most in NA are Very High. EU is either Very High or High/Med, I believe.
http://wiki.guildwars2.com/wiki/Extended_Online_Manual
https://www.guildwars2.com/en/the-game/releases/
Best to just jump in and discover the world, as that is probably the most fun to be had.
Welcome return.
This is a recap of what happened Story Wise during the Season 1 of the Living Story:
http://wiki.guildwars2.com/wiki/Living_World_season_1
This lists all releases and the mayor content updates that were introduced with them:
http://wiki.guildwars2.com/wiki/Game_releases
I think Warrior is quite an easy class for a beginner and there usually is at least 1 in every group.
If you are interesting in WvW, you might want to check out, if the server you are on has an active community and player base. If you would like to do WvW in the future but are on a server with a low wvw population, you might want to consider to delete all your characters now and choose a different home server. If you delete all your characters, the server transfer is free but if you decide to transfer with your characters at a later stage, it can cost up to 1800 gems.
Bloin – Running around, tagging Keeps, getting whack on Scoobie Snacks.
It’s probably a good moment to jump back in, since season 2 of LS is just started and so far it proves to be a BIG improvement over the season one, especially episode 2.
Engi is probably still the most underplayed class. PvE wise most popular classes for group play are guardians, mesmers, warriors, eles.