Torhead shut down because it wasn't updated. Torcommunity or tor-community dot com has similar info in terms of item database, or at least as close as anyone else as far as I know. Dulfy.net has a lot of content like content/quest guides (tor-community also has their own guides I believe, both tend to apply just to the latest content but older quest guides may be found) and rotation information (that is either 4.0 updated or "should be soon" (no idea of tc has that). Tor-fashion.com can help you figure out different armor you might want to acquire. It normally tells how to acquire the different pieces of gear. The swtor subreddit will also have good info though not always in guide format. As far as figuring out how to finish class quests and main story quests, those are usually self explanatory with good use of the map. Googling the quest name will normally help you find solutions to possible bugs if you encounter any.