Returning to ESO & I haven't played since Jan 2014 looking for advice on upgrading account

Solution 1:

Extra content for Elder Scrolls Online comes in 4 variants:

• Free updates: every player gets these regardless of account type;
• Crown Store Upgrades: smaller convenience or flexibility upgrades available for the premium currency;
• DLC Game Packs: You get these automatically if you're a subscriber, or you can buy them for crowns at the ingame shop;
• Chapters: major story upgrades that you need to buy separately.

Morrowind was originally a Chapter. However, with the release of the next Chapter, Summerset, Morrowind was made no longer available for purchase divided into several smaller components:

• Battlegrounds have become part of the base game;
• The Warden class has turned into a separate Crown Store Upgrade, available for 1500 Crowns;
• Vvardenfell, the new zone, has turned into a DLC Game Pack, which is included with the subscription fee or can be bought from the Crown Store.

So if you want to play the Warden class, all you need to do is buy the Upgrade from the Crown Store for 1500 crowns.