I am pretty sure if you didn't know what an Ewok was, you would be fine, you would just find out later on that they were the same people in the Return of the Jedi. EVERY, EVERY quest in SWTOR is voiced. And it is made by Bioware that likes for its chars to chat on and on about stuff. So if you are interested in lore, you should be fine with just the game. I think you can just skip the voice part if you don't want to wait for the chars to tell you how they washed their laundry last week... "Quest: Find clean clothes." Or how they have a very special diet and haven't eaten so good since they were on the farm back on ...... "Quest: Collect tasty grubs."
They put it in a different time period than the movies, but it can't hurt to watch them to get the general stuff.