Comming back after over 2 years
You likely have to pick your armor stats because you had magic find involved. This stat was removed from armor.
Spend your Hero Points to re-unlock your skills and traits. You can have 3 traitlines active at a time, all the way to grandmaster level. Since you are level 80 you should have enough points to do this, no problem, especially if you were anywhere close to map completion.
Your two crafting disciplines can go up to 500 now with the ascended tier of mats. Doing content in game will give you different mats (bloodstone, empyrials, dragonite) For now all you can craft is ascended weapons and armor. Make sure you have plenty of Obsidian Shards.
I hope you already had your precursor for The Dreamer, as the price has jumped considerably since you last played.
If you don’t have map completion, you no longer need to bother with exploring the WvW maps for this.
Server transfers are no longer free, and guesting is no longer a thing. You only really need these for WvW content, as the rest of the PvE game is on the megaserver system. Transfers are available from the character select screen, and cost a boatload of gems last I checked (2k?)
A couple of other points:
check your “wallet” (icon in the lower left of your inventory.) Many drops and currencies have been consolidated here. If you are missing stacks of things you used to have, check here first.
Condition damage has been changed as well, as you no longer have to compete with others for stacks. All of your damage will now be applied.
There are new fractals and several new maps for you to explore (dry top, silverwastes, etc) These are great places to farm for gold / mats to help you on your legendary quest.
There are tons of new achievements, check them out.
It’s possible to transfer to another server for free but it requires you to delete all your char. Because the game has megaservers now, the only reasons to change are because of WvW or EU <—> NA.
ANet may give it to you.